Remove the Windows 7 (7.css) skin

The win7 skin is dropped. Everything else the branch built stays: Linux
support and the HTML context menus, the workspace-tab menu, the continuous
interface scale (rem everywhere, stepper, Ctrl/Cmd +/-/0) and the core/
service layer. The modern tree already carried all of them, and nothing
outside skins/7like/ imported the win7 tree except main.ts and styles.css.

Removed: the skins/7like/ tree (5.1k lines, fonts), the 7.css dependency,
the skin setting and its options row + strings in all 7 locales, the
frameless-window plumbing (window-control RPCs, windowState push,
trackMaximizeState, the synthesized resize grip and its postinstall
watchdog), the session-skin pinning in buildPreload/chromeOptions, the
skin/skinfix cascade layers, and the win7-only probes and screenshot
harness (the harness cannot render the modern tree: plain Firefox has no
RPC bridge). chromeOptions() stays as the one shared frame decision.

Fixed on the way out:
- index.html's per-theme pre-paint background is restored. The branch had
  replaced it with a win7-only transparent rule, so modern dark windows had
  silently lost one of the three flash guards.
- editor-windows.ts wrote its window-key separator as a literal NUL byte,
  which made git and grep treat the file as binary; it is `\0` now (same
  string at runtime).

No settings migration: a stale "skin" key is carried harmlessly by the
store's spread-merge and dropped on the next save.

UI bundle: 616.7 kB -> 405.4 kB, back under the 500 kB budget.

Docs: architecture, gotchas and platform-notes lose the win7 material but
keep what stays true (construction-time preloads/frames, drag regions
ignoring preventDefault, electrobun's missing resize/maximize primitives);
flash-prevention, dev-URL and Bun-panic notes move back under Electrobun;
stale context-menu/tab-bar links fixed; README documents the scale keys.

Co-Authored-By: Claude <noreply@anthropic.com>

docs/gotchas.md

@@ -28,17 +28,6 @@ touching the adjacent code.
 - Tailwind v4 canonical class names: `wrap-break-word` not `break-words`,
   `accent-primary` not `accent-[var(--primary)]`, `z-60` not `z-[60]`.
   Every color used in a template must resolve through `@theme inline`.
-- **The win7 skin layer outranks Tailwind utilities.** 7.css is imported
-  `layer(skin)`, ordered above `utilities`, so any utility you add to a
-  `button`/`input`/`select`/`textarea`/`table` is silently dead under that
-  skin. If it matters, neutralize in the `@layer skin` block in
-  `app/skins/7like/7like.css` — and note `revert-layer` only reaches
-  `utilities` from **inside `skin`**; used from `skinfix` it falls back onto
-  7.css and is a no-op. This bit once already.
-- `@import … layer(name)` works through `@tailwindcss/postcss` (it wraps the
-  imported AST), but the **deep path is mandatory**: 7.css ships no `exports`
-  map and Tailwind's resolver reads only `style`/`mainFields`, so a bare
-  `@import "7.css"` resolves to nothing. Use `7.css/dist/7.scoped.css`.
 - Stylesheet `url()` must resolve at BUILD time: assets referenced from
   `styles.css` live under `ui/src/` (esbuild emits them hashed into `media/`
   and rewrites the url), NOT `ui/public/` — a public path fails the build with
@@ -53,6 +42,18 @@ touching the adjacent code.
 - **A component `template:` is a TS template literal, so no backticks inside
   it** — not even in an HTML comment. A backtick in a comment terminates the
   literal and the errors point at the prose, not at the quoting.
+- **Reach `core/` through the `@core/*` alias, never a relative path.**
+  Components sit at varying depths and get moved; the alias is what let 67
+  imports survive two relocations untouched. A `../../core/...` path is a
+  future merge conflict.
+- **The build DOES type-check components nothing imports.** ngtsc compiles the
+  whole program, so an unreferenced component still fails `bun run build:ui` on
+  a type or template error (verified by injecting an error into an
+  unreferenced file).
+- **`overflow-x: auto` also clips vertically.** CSS refuses to pair `visible`
+  with a non-visible axis, so the computed `overflow-y` becomes `auto` too:
+  anything poking out of a horizontally scrolling strip (a raised tab, an
+  underline at `-bottom-px`) is silently clipped. Reserve padding instead.
 
 ## The interface scale (root font-size lever)
 
@@ -66,137 +67,16 @@ touching the adjacent code.
   JSDoc's "(WebKit only)" means macOS WKWebView. This is why the scale is CSS.
 - **Everything the UI sizes with must be rem.** The scale works by setting the
   root font-size, so a px value freezes while everything around it grows. The
-  three px reservoirs were: the panel-chrome tokens (`--row-h` etc.), 93
-  `text-[11px]` arbitraries, and 7.css itself — 370 px values, zero rem, with
-  `--w7-font` reaching only 15 rules' typography. 7like.css's `skinfix` carries
-  a scale bridge re-expressing 7.css's vars and hardcoded box metrics in rem.
-  1px hairlines and focus rects stay px deliberately (crisp at any scale; the
-  `tr` border exists to stop selection shifting rows).
-- **Restating a 7.css rule in `skinfix` also outranks 7.css's VARIANTS of that
-  rule — by layer, regardless of specificity.** The title-bar-controls
-  restatement silently shrank the close button from 48px to 29px (7.css widens
-  it via `button[aria-label=Close]`), and the tablist padding flattened the
-  active tab's 4px raise. Caught only by the harness pixel diff. When bridging
-  a rule, grep 7.scoped.css for every variant that overrides the same
-  properties and restate those too.
+  px reservoirs were the panel-chrome tokens (`--row-h` etc.) and 93
+  `text-[11px]` arbitraries. 1px hairlines and focus rects stay px deliberately
+  (crisp at any scale).
 - **px constants in TS that mirror rem-sized CSS are latent scale bugs.** The
-  shadlike context menu's `MENU_W = 224` was a hardcoded mirror of `w-56`
+  context menu's `MENU_W = 224` was a hardcoded mirror of `w-56`
   (14rem): box grew, math didn't, flip fired at the wrong edge. Convert through
   `@core/metrics` `remPx()` at use time — it reads the LIVE root font-size,
   and per call, since the scale changes mid-session. The editor's canvas-based
   `charWidth` is cached keyed on the computed font string for the same reason.
 
-## Hover states and the frame edge
-
-- **A child's box-shadow is NOT clipped by its parent's border or radius.** The
-  close button's hover glow (7.css: `0 0 7px 3px #e68e75` on a `::before`)
-  painted across the window's top border and onto the desktop beyond it — the
-  caption buttons sit flush against the top edge (`border-top: 0`), and the
-  frame's rounded transparent corners clip nothing. Fixed with
-  `clip-path: inset(0 0 -1rem 0)` on `.w7-frame > .title-bar`: glow stops at
-  the frame like the real DWM, bottom bleed (authentic) stays open. Note
-  clip-path also clips hit-testing — safe here because the drag region is the
-  title-bar's own box, entirely inside the clip.
-- **Hover states CAN be tested headlessly**: `scripts/hover-probe.ts` copies
-  the built stylesheet with `:hover` rewritten to `.simhover`, renders the
-  frame markup with the state forced, and pixel-scans artifact regions,
-  exiting non-zero on hover-introduced red outside the frame. Firefox
-  `--screenshot` has no pointer and `import -window` captures the real
-  pointer's state, so the class rewrite is the only programmatic hover on this
-  machine. Re-run it after touching title-bar or hover styling.
-
-## The two skin trees (`ui/src/app/skins/`)
-
-- **`.win7` is not a name we may change.** `7.scoped.css` is precompiled with
-  every selector prefixed by that literal class, so the skin id in
-  `AppSettings` stays `"win7"` even though its folder is `7like/`. The folder
-  names are cosmetic; the class and the persisted setting value are not.
-- **Reach `core/` through the `@core/*` alias, never a relative path.** Skin
-  components sit at varying depths and get moved; the alias is what let 67
-  imports survive two relocations untouched. A `../../core/...` path is a
-  future merge conflict.
-- **`@font-face` `url()` resolves relative to the file that declares it.** When
-  the win7 rules moved three directories deeper, `./fonts/...` would silently
-  have 404'd — build still green, app just renders a fallback font. The fonts
-  therefore live inside the skin that uses them.
-- **The `@layer` statement must stay the first statement in `ui/src/styles.css`.**
-  It is one of only two rule types allowed above `@import`, and it is what sorts
-  `skin` above `utilities`. Every `@import` (Tailwind and both skin sheets) must
-  also precede all other rules.
-- **Duplicate selectors across skins are safe.** `app-file-panel` exists in both
-  trees; standalone components resolve through their importer's `imports:`
-  array, never a global registry, and the trees are never mounted together.
-- **The build DOES type-check components nothing imports.** ngtsc compiles the
-  whole program, so a skin that is currently unreachable still fails
-  `bun run build:ui` on a type or template error. Verified deliberately by
-  injecting an error into an unreferenced file — worth knowing before assuming
-  a green build proves nothing about the inactive skin.
-
-## The win7 skin (7.css)
-
-- **Unlayered declarations beat every `@layer`, regardless of specificity.**
-  `html, body { background: … }` in styles.css is unlayered, so no `skinfix`
-  rule can override it — the win7 transparent-corner reset has to be unlayered
-  too. The frame's rounded corners only read as rounded because nothing paints
-  an opaque full-bleed ground behind them; anything that does fills the corners
-  and the window becomes a rectangle with a curve drawn on it.
-- **7.css restates `border-color` at (0,3,1)** via
-  `.win7 button:not(:disabled):not(:hover)` and its `:hover` twin. A two-class
-  selector like `.win7 .w7-flat` (0,2,0) loses to it, so paint suppression for
-  flat buttons lives in `skinfix` where layer order settles it. The
-  `.w7-toolbar` arm only ever won by tying on specificity and landing later in
-  the same layer — an accident `w7-flat` did not share, which is why it
-  rendered a bordered slab while its neighbours went flat.
-- **`overflow-x: auto` also clips vertically.** CSS refuses to pair `visible`
-  with a non-visible axis, so the computed `overflow-y` becomes `auto` too.
-  7.css raises the active tab with `margin-top: -2px`; inside the horizontally
-  scrolling tab strip that put its top border outside the scroll box and
-  deleted it silently. The strip reserves `padding-top: 2px` to compensate —
-  mirroring the `padding-left: 3px` 7.css already reserves for the same tab's
-  `-3px` left margin.
-- **7.css hardcodes light-mode literals outside its own var system** —
-  `color: #222` on tablist buttons, black/white bevels in the ListView and
-  menu. Each one has to be routed through a `--w7-*` token declared in
-  `:root.win7` and overridden in **both** dark blocks (the `[data-theme]`
-  attribute one *and* the `prefers-color-scheme` one; system dark sets no
-  attribute).
-- **The skin layer can also override `position`, and that breaks LAYOUT, not
-  just paint.** `ul[role=menu]` carries `position: relative` in 7.css (for the
-  gutter stripe's `::before` and submenu anchoring), which outranked Tailwind's
-  `.fixed` on the app's own context menu. `[style.left/top.px]` then became
-  *flow* offsets from the menu's static position — the last child of the
-  `h-screen` frame — so every right-click menu rendered below the viewport,
-  unreachable behind `overflow: hidden`. The backdrop is a plain `<div>`, which
-  7.css does not match, so it stayed genuinely fixed and ate the next click:
-  the symptom was "right-click does nothing, then the app ignores me once".
-  Fixed with a `position: fixed` restatement in `skinfix`, scoped to a `w7-ctx`
-  marker class so 7.css's own menus keep theirs. Regressed in `0ae2a62`, when
-  the menu root became a real `ul[role=menu]` — i.e. adopting the framework's
-  markup is what exposed it. **A resting pixel diff cannot catch this class of
-  bug**: nothing about the idle window changes. `scripts/menu-probe.ts` renders
-  the menu at declared coordinates and scans whether it landed there, with a
-  marker-less control menu as its own discriminator.
-- **7.css's button effects reach anything that IS a button — including menu
-  items — and one of them fades out over a FULL SECOND.** `button::before` is
-  an Aero glow overlay with `opacity: 0`, raised to 1 on hover, and
-  `button:not(:hover):before` carries `transition: opacity 1s linear`.
-  menu.css suppresses it with `content: none` on the **`:hover` arm only**, so
-  while an item is hovered nothing paints, but the moment the pointer leaves,
-  the pseudo returns with opacity animating 1 → 0: a blue ghost trailing the
-  cursor down the menu. Killing `content` in *every* state is the fix —
-  suppressing the transition alone leaves a glow that simply snaps. Two more
-  from the same family: `button:focus` runs `pulse-anim` *infinitely*
-  (`1s ease infinite alternate`), which matters because the context menu moves
-  REAL focus between items for keyboard nav, and the hover paint is 7.css's
-  translucent gradient wash — the same one the ListView selection dropped.
-  All three are overridden together, scoped to `w7-ctx`.
-- **Its selectors are exact, and a near-miss looks exactly like "7.css doesn't
-  support this".** `menu[role=tablist] button` is a DESCENDANT selector, so
-  every button inside the strip becomes a tab — the `+` and the right-hand
-  tools must live outside it. `.window.glass > .title-bar` is direct-child, so
-  an inner wrapper breaks the glass coupling. A wrong guess here already
-  produced one hand-written lookalike that was deleted.
-
 ## Electrobun
 
 - **Window `close` is not cancellable** (response type `{}`; only the
@@ -221,9 +101,48 @@ touching the adjacent code.
   `dist/api/bun/proc/linux.md` says so; the app also prints "Application menus are
   not supported on Linux" at boot). Because the UI suppresses the webview's own
   right-click menu, that left EVERY panel context menu dead on Linux — no error,
-  nothing happens. The menu is plain HTML now (`ui/src/app/skins/*/context-menu.ts`) on
+  nothing happens. The menu is plain HTML now (`ui/src/app/skins/shadlike/context-menu.ts`) on
   every platform; don't reintroduce the native one for "nativeness" on mac/win
   without keeping a Linux path.
+- **Window-open flash prevention is three-layer** — remove any one and the
+  white/inverted blink returns: (1) windows are created `hidden: true` and
+  revealed by `showWhenReady` on the webview's first `dom-ready` (800 ms
+  fallback), (2) the bun preload bakes the persisted `data-theme`/tone/accent
+  attributes and the interface scale before first paint (`buildPreload`),
+  (3) `ui/src/index.html` carries an inline `<style>` with the html background
+  per theme — its oklch values MUST stay in sync with the `--background` tokens
+  in styles.css. (The win7 branch once replaced (3) with a transparent rule and
+  the modern skin silently lost it — the other two layers do not cover it.)
+- Dev vs prod URL: `getMainViewUrl()` resolves the ng-serve dev server only
+  when `DEV_SERVER_URL` is set AND the updater channel is `dev` AND the
+  server answers a HEAD request; secondary windows must reuse the resolved
+  URL, never hardcode `views://`.
+- Upstream Bun panic (`FFI_Callback_threadsafe_call` → `web_worker.spin`):
+  rare segfault under long sessions; upstream electrobun×Bun issue, restart
+  recovers, nothing app-side to fix.
+- **Preloads and frames are construction-time only.** The preload is a
+  persistent `WebKitUserScript` at DOCUMENT_START, frozen at webview
+  construction — `webview.loadURL()` re-runs the OLD one
+  (`updatePreloadScriptToWebView` is only reachable from electrobun's internal
+  `<electrobun-webview>` handler). `titleBarStyle`/`transparent` have no
+  setters. Anything `buildPreload` bakes is a first-paint snapshot the UI must
+  correct live over RPC. Recreating the main window is not an escape hatch:
+  `exitOnLastWindowClosed`, push closures and the tray capture it, and there
+  is no `off()`.
+- **Drag regions ignore `preventDefault`.** The preload starts a window move
+  from a bubble-phase `mousedown` on `document` and never reads
+  `defaultPrevented`; a `pointerdown` handler doesn't stop it either (the
+  compat `mousedown` still fires). `isAppRegionDrag` checks
+  `.electrobun-webkit-app-region-no-drag` first — that class on the element is
+  the only reliable suppressor (`dist/api/bun/preload/dragRegions.ts`).
+- **No resize, maximize-event or double-click-maximize primitives (1.18.1).**
+  `titleBarStyle: "hidden"` drops the whole frame (Cocoa `Titled` — the only
+  way to remove the traffic lights; `gtk_window_set_decorated(false)` on
+  Linux) and with it the WM resize borders; nothing restores them (no
+  `startWindowResize`, no `gtk_window_begin_resize_drag`, no
+  `setResizable`/min-size options — only `setFrame`/`getFrame`). No maximize
+  event exists (derive it from `resize` + `isMaximized()`), and drag regions
+  don't double-click-maximize. A custom-chrome window has to build all three.
 
 ## Linux
 
@@ -266,100 +185,13 @@ touching the adjacent code.
   pattern appears in the killing command's OWN argv. Break the literal with a
   character class — `pkill -f 'dev-linux-x[6]4'` — the way `ps | grep [x]yz`
   has always worked.
-- **A frameless window cannot be resized, and `preventDefault` will not save
-  you from the drag region.** Undecorating the GTK window (what
-  `titleBarStyle: "hidden"` does) takes the WM's resize borders with it, and
-  electrobun exposes no resize gesture — hence the synthesized grip in
-  `ui/src/app/skins/7like/window-resize/` (a STOPGAP; that file carries the
-  removal checklist, and `scripts/check-electrobun-resize.ts` fires from
-  `postinstall` when upstream makes it deletable).
-  **An invisible resize handle over a control steals that control's hover.** A
-  full eight-handle set shipped briefly and was reverted: the north strip ran
-  the whole width across the caption buttons and the north-east square sat on
-  the close button's corner, so crossing one dropped the button's `:hover`
-  mid-glow and looked like a rendering artifact in 7.css — nothing in the CSS
-  was wrong. Only the bottom-right corner overlaps nothing (it lands in the 6px
-  gutter `.window-body { margin: 0 6px 6px }` leaves). Any new handle must be
-  checked against what sits under it; south/east/west are innocent, north and
-  both top corners are not.
-  Three more traps live in that code, all verified against
-  `dist/api/bun/preload/dragRegions.ts`:
-  - It starts a window **move** from a `mousedown` listener on `document`, in
-    the **bubble** phase. It never reads `defaultPrevented`, so
-    `event.preventDefault()` does **nothing** to stop it.
-  - A `pointerdown` handler does not stop it either: the compatibility
-    `mousedown` still fires afterwards, and stopping propagation on a *pointer*
-    event has no effect on a *mouse* event. This is the trap that looks fixed
-    in every test until the window jumps.
-  - `isAppRegionDrag` checks `.electrobun-webkit-app-region-no-drag` **first**
-    and short-circuits, so that class — on the handle itself — is the only
-    reliable suppressor. Without it, every resize drag also drags the window.
-  Also: deltas must come from `screenX/screenY`. North/west resizes move the
-  window's origin, which moves the webview's client origin under a stationary
-  pointer, so `clientX` feeds that movement back into the next delta and the
-  window runs away. And the minimum-size clamp must re-anchor the opposite
-  edge — clamping the width alone lets `x` keep tracking the pointer, walking
-  the window off-screen while it looks frozen (`scripts/resize-math-probe.ts`
-  asserts exactly that, and was verified to catch it).
-- **Prefer the headless probes over launching the app.** `bun run start` opens a
-  real window that takes focus, which interrupts whatever the user is doing;
-  there is no Xvfb/xvfb-run on this machine and Wayland offers no
-  launch-without-focus. `scripts/shot.ts` (+ `--dark`), `hover-probe.ts` and
-  `menu-probe.ts` all render through headless Firefox and open nothing. Launch
-  the real app only for what Gecko genuinely cannot answer — WebKitGTK
-  behaviour, the native frame, transparency, live RPC — ask first, and batch
-  every live check into a single launch.
-- **X11 capture cannot answer "is this pixel transparent?"** for the frameless
-  window. `import -window` grabs the window's own pixels with no compositing,
-  so a transparent corner and an opaque black one both come out black;
-  `png32:` just fills alpha with 1 and proves nothing. XWayland's root window
-  is not the composited desktop, so `import -window root` fails too. Frame
-  transparency and the maximized corners need a human looking at the screen —
-  say so rather than reporting a screenshot as confirmation.
+- **Launching the app steals focus — ask first.** `bun run start` opens a real
+  window that takes focus, which interrupts whatever the user is doing; there
+  is no Xvfb/xvfb-run on this machine and Wayland offers no
+  launch-without-focus. Batch every live check into a single launch.
 - Benign startup noise on Linux — non-fatal, the app runs normally:
   `libayatana-appindicator is deprecated. Please use libayatana-appindicator-glib`
   (upstream electrobun's choice, not ours).
-- **Window-open flash prevention is three-layer** — remove any one and the
-  white/inverted blink returns: (1) windows are created `hidden: true` and
-  revealed by `showWhenReady` on the webview's first `dom-ready` (800 ms
-  fallback), (2) the bun preload bakes the persisted `data-theme`/tone/accent
-  attributes before first paint (`buildPreload`), (3) `ui/src/index.html`
-  carries an inline `<style>` with the html background per theme — its oklch
-  values MUST stay in sync with the `--background` tokens in styles.css.
-  The win7 skin adds a **fourth value to keep in sync**: `buildPreload` also
-  bakes the `.win7` class, and index.html carries a matching `html.win7` arm
-  for all four theme states. Miss it and every win7 window flashes white.
-- **The skin is a LAUNCH-TIME choice. Never apply one to a running window.**
-  This shipped broken once: `SettingsService.applySkin` toggled the `.win7`
-  class the moment the setting changed, which was harmless when there was one
-  component tree and became a broken window as soon as there were two — 7.css
-  painted onto shadlike markup that has no `.window.glass`, no `.title-bar`, no
-  `menu[role=tablist]` and no `<table>` ListView. Each skin's CSS is written
-  against its OWN tree's markup; the class must only ever be written by
-  `buildPreload`, for the tree that window actually booted.
-  - **A reload does not rescue it.** The preload is a persistent
-    `WebKitUserScript` injected at DOCUMENT_START, so its string is frozen at
-    webview construction — `webview.loadURL()` re-runs it with the OLD
-    `__APP_SKIN`. (`updatePreloadScriptToWebView` exists in the FFI but is
-    reachable only from electrobun's internal `<electrobun-webview>` handler.)
-  - **`titleBarStyle`/`transparent` are construction-time only** — no setters
-    exist, so a live window can never be re-framed. win7 → modern is the
-    dangerous direction: the modern tree draws no title bar, so it would land
-    in a frameless transparent window with no way to move, minimize or close.
-  - Don't "fix" this by recreating the main window either: `exitOnLastWindowClosed`
-    is true, the main `rpc` is captured by six push closures, the tray captures
-    `win`, listeners cannot be removed (no `off()`) — and it would drop every
-    session and tab.
-  - Bun pins it: `initSessionSkin` freezes the skin before any window exists,
-    and `buildPreload`/`chromeOptions` read that, never the live settings. Skip
-    the pin and a window opened after a pending change boots the other skin.
-- Dev vs prod URL: `getMainViewUrl()` resolves the ng-serve dev server only
-  when `DEV_SERVER_URL` is set AND the updater channel is `dev` AND the
-  server answers a HEAD request; secondary windows must reuse the resolved
-  URL, never hardcode `views://`.
-- Upstream Bun panic (`FFI_Callback_threadsafe_call` → `web_worker.spin`):
-  rare segfault under long sessions; upstream electrobun×Bun issue, restart
-  recovers, nothing app-side to fix.
 
 ## Domain logic