Make w7-flat actually flatten; document this round

The status bar's transfers summary is a text toggle, but 7.css painted it as
a full Aero push button — a stray bordered slab sitting in the status line.
Marked it w7-flat, the per-button escape hatch that existed for exactly this
and had never been used.

It did not work, for a reason worth keeping: 7.css restates border-color at
`.win7 button:not(:disabled):not(:hover)` = (0,3,1), which outranks
`.win7 .w7-flat` = (0,2,0). The .w7-toolbar arm of the same rule only ever
won that fight by tying on specificity and landing later in the same layer —
an accident w7-flat did not share. Split the rule: `background:
revert-layer` stays in `skin` (it must land on `utilities`), and the
paint-suppression literals move to `skinfix`, where layer order settles it
instead of a specificity arms race.

Docs updated in the same change per the working agreement — architecture.md
gains the tabs contract, the w7-flat/w7-toolbar split and the frame
transparency invariant; gotchas.md gains a win7-skin section (unlayered beats
every layer, the (0,3,1) border-color restatement, overflow-x clipping the
y-axis, 7.css's hardcoded light literals, exact selectors) plus the two
Angular traps this round hit: a duplicate `class` attribute is silently
dropped, and a backtick inside a component template's HTML comment terminates
the TS template literal.

Also recorded the verification trap that cost three wrong readings today:
`bun run start` leaves the old instance running and `import -window` grabs
the OLDEST match, so screenshots silently come from a stale build — this is
what made the w7-flat fix above look like a no-op when it was already
correct. Kill and count instances before capturing. And `pkill -f
'electrobun dev'` matches the shell running it and kills your own command.

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

docs/gotchas.md

@@ -43,6 +43,51 @@ touching the adjacent code.
   `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
   "Could not resolve".
+- **Two `class` attributes on one element: the second is silently dropped.**
+  No warning, no build error — the layout classes simply never apply. This
+  collapsed the tab strip and two window headers at once (`fe028a9`), because
+  a scripted edit appended `class="…"` to elements that already had one.
+  When removing a conditional binding, check what the branch *contained*: the
+  bindings there were genuinely dead, but the layout classes inside them were
+  not, and nothing replaced them.
+- **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.
+
+## 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).
+- **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
 
@@ -100,6 +145,22 @@ touching the adjacent code.
     an explicit `WEBKIT_DISABLE_DMABUF_RENDERER` from the user always wins.
   - A "does it boot?" log check does NOT catch this — grep for the GBM line, or
     look at the window.
+- **`bun run start` leaves the old instance running, and
+  `import -window miniSCP` grabs the OLDEST match.** Instances pile up across
+  rebuilds, so every screenshot silently comes from a stale build and the fix
+  you just made looks like it did nothing. Cost three wrong readings in one
+  session, including a "the CSS is in the bundle but does not apply" dead end.
+  Kill first (`pkill -f dev-linux-x64`), confirm with
+  `pgrep -cf 'dev-linux-x64/miniSCP-dev/bin/launcher'`, then launch and capture.
+  Note `pkill -f 'electrobun dev'` also matches the shell running it and kills
+  your own command (exit 144) — match on the build path instead.
+- **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.
 - 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).