Scale stage 1: everything the UI sizes with is now rem

Groundwork for the continuous interface scale (a root font-size lever): every
size the UI derives from must be root-relative, or it freezes while the rest
grows. Gate for this commit: at the default 16px root the app renders
pixel-identical to before — every conversion is exact (11px = 0.6875rem …).

- The 8 panel-chrome tokens in styles.css: px -> rem, and the data-text
  compact/large tiers are DELETED — a continuous scale replaces discrete
  tiers. Same for --w7-fs (12px -> 0.75rem) and the win7 --radius (5px ->
  0.3125rem, still landing rounded-md exactly on --w7-el-bdr's 3px).
  --radius-sm/md subtrahends: px -> rem, or corners would sharpen as the UI
  grew.
- All 93 text-[11px]/text-[10px] arbitraries -> rem equivalents, plus the two
  inline padding:24px empty-state cells in the 7like file panel.
- 7like.css gains a scale bridge in skinfix: 7.css is 370 px values with zero
  rem, and --w7-font reaches only 15 rules' TYPOGRAPHY — under a root lever
  win7 text would grow inside boxes frozen at 23px/14px/15px. The bridge
  re-expresses 7.css's size vars and its hardcoded box metrics (buttons via
  .w7-btn only, inputs, table rows/headers, title-bar controls, menu items,
  tabs, the 10pt check glyph) in rem at identical scale-1 pixels. 1px
  hairlines and focus rects stay px deliberately — crisp at any scale, and
  the tr border exists precisely to stop selection shifting rows.
- Two skinfix traps found while writing it, one by reasoning and one by
  pixels: (a) NO blanket `.win7 button` restatement — skinfix outranks the
  skin-layer neutralizer that strips 7.css's 75x23 metrics off the ~84 icon
  buttons, so a blanket rule would re-inflate them all; (b) restating a base
  rule in skinfix also outranks 7.css's own VARIANTS of it by layer — the
  title-bar rule silently shrank the close button from 48px to 29px until the
  harness pixel diff caught it, and the active tab's padding-bottom needed
  the same treatment. Both variants are restated alongside their base rules.
- TS px constants that mirror rem CSS are the latent-bug half of this work:
  both context menus' flip/clamp math converts through a new @core/metrics
  remPx() helper reading the LIVE root font-size (the shadlike menu's
  MENU_W=224 diverged from its w-56 box the moment scale != 1; the 7like
  menu's [style.width.px] pinned the box at 200px while text grew — it now
  binds width in rem, so math and box cannot disagree). The editors'
  cachedCharWidth is now keyed on the computed font string, self-invalidating
  under any font change, and both || px fallbacks derive from the element's
  font size instead of assuming a 16px root.

Verified: tsc + build clean; modern and win7 live captures and the harness
all diff to zero against pre-change baselines in their opaque regions (the
harness to exactly zero end to end; modern's only delta is the native GTK
titlebar focus state; win7's is the translucent Aero corner over the
desktop).

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

ui/src/app/skins/shadlike/dialogs/overwrite-dialog.ts

@@ -30,7 +30,7 @@ import { FocusService } from '@core/focus.service';
           </h2>
           @if (request().total > 1) {
             <span
-              class="shrink-0 rounded-full bg-muted px-2 py-0.5 text-[10px] font-medium text-muted-foreground"
+              class="shrink-0 rounded-full bg-muted px-2 py-0.5 text-[0.625rem] font-medium text-muted-foreground"
             >
               {{ i18n.t('dialogs.ofTotal', { index: request().index, total: request().total }) }}
             </span>
@@ -49,11 +49,11 @@ import { FocusService } from '@core/focus.service';
           @for (side of comparison(); track side.label) {
             <div class="rounded-md border border-border p-2.5">
               <div class="flex items-center justify-between">
-                <span class="text-[10px] font-medium tracking-wide text-muted-foreground uppercase">
+                <span class="text-[0.625rem] font-medium tracking-wide text-muted-foreground uppercase">
                   {{ i18n.t('dialogs.' + side.label) }}
                 </span>
                 @if (side.newer) {
-                  <span class="rounded-full bg-success/15 px-1.5 text-[10px] font-medium text-success">
+                  <span class="rounded-full bg-success/15 px-1.5 text-[0.625rem] font-medium text-success">
                     {{ i18n.t('dialogs.newer') }}
                   </span>
                 }
@@ -68,7 +68,7 @@ import { FocusService } from '@core/focus.service';
                   {{ isDir() ? '—' : i18n.size(side.entry.size) }}
                 </span>
               </div>
-              <div class="mt-1 font-mono text-[11px] tabular-nums text-muted-foreground">
+              <div class="mt-1 font-mono text-[0.6875rem] tabular-nums text-muted-foreground">
                 {{ i18n.date(side.entry.mtime) }}
               </div>
             </div>