Stage 2: file panels become a real 7.css ListView

The file list was a CSS grid of <div>s, so 7.css's listview component never
matched a single selector and Tailwind styled the whole thing. It is now the
plain <table> 7.css documents, which is what makes the Aero treatment appear.

- The column header row moved OUT of its own div and INTO <thead>: 7.css makes
  thead position:sticky, so it stays put while the body scrolls, and it has to
  be inside the same table to do that.
- Column widths moved from a computed grid-template-columns to <colgroup>,
  because 7.css sets table-layout: fixed. `gridTemplate()` is deleted.
- Selection is now `tr.highlighted` (7.css's gradient band + #aaddfa border)
  instead of bg-primary/15.
- The sort arrow was the text glyph ↑/↓ from `sortIndicator()`, which is also
  deleted; the sorted column is now `th.highlighted.indicator[.up]` and 7.css
  draws the real clip-path triangle in the header.
- Row height, padding, borders and fonts now come from 7.css, so --row-h and
  the per-cell text/color/font utilities are gone.

Two things 7.css does not cover, added in `skinfix`:
- Dark mode. listview.css hardcodes light literals (#fff, #c0c1cd, #eee and a
  white header gradient) rather than --w7-* vars, so it does NOT follow the
  hand-authored dark palette — the header labels rendered invisible, dark on
  dark. The dark arms restate those rules; light keeps 7.css's own values.
- The keyboard cursor. 7.css models selection only; Win7 drew the focused row
  with a dotted focus rectangle over it, which is what tells "cursor" apart
  from "selected" when they differ. That is `tr.is-cursor`.

Verified visually this time, not just by build log: harness screenshots in both
light and dark show the header gradient, sort triangle, cell separators,
selection band and cursor rectangle matching 7.css's reference markup. Backend
`tsc --noEmit` clean, `bun run build:ui` clean, bundle 489.83 kB (from 490.50).

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

ui/src/styles.css

@@ -598,13 +598,43 @@ body {
    neighbouring layer. */
 @layer skinfix {
   /* Opt back IN to real Win7 push-button metrics, for the dialog and options
-     buttons where they are right. Inert under the modern skin. */
+     buttons where they are right. */
   .win7 .w7-btn {
     min-width: 75px;
     min-height: 23px;
     padding: 0 12px;
   }
 
+  /* ---- ListView (file panels) ----
+     7.css's listview.css hardcodes light literals (#fff, #c0c1cd, #eee and the
+     white header gradient) instead of --w7-* vars, so unlike the rest of the
+     skin it does NOT follow the hand-authored dark palette — the header labels
+     came out invisible, dark on dark. These restate the same rules in dark
+     terms; they are scoped to the dark arms only so light keeps 7.css's own
+     values untouched. */
+  .win7[data-theme='dark'] table,
+  .win7[data-theme='dark'] table > tbody > tr > * {
+    background-color: var(--w7-el-bg-s-2);
+    border-color: var(--w7-el-bd-d);
+    color: var(--w7-el-c);
+  }
+  .win7[data-theme='dark'] table > thead > tr > * {
+    background: linear-gradient(180deg, var(--w7-el-bg) 45%, var(--w7-el-bg-d) 0, var(--w7-el-bg-s-1));
+    border-color: var(--w7-el-bd-d);
+    color: var(--w7-el-c);
+  }
+  .win7[data-theme='dark'] table > tbody > tr > :not(:last-child) {
+    border-right-color: var(--w7-el-bd-d);
+  }
+
+  /* The keyboard cursor. 7.css models only selection (tr.highlighted); Win7
+     drew the focused row with a dotted focus rectangle on top of it, which is
+     what distinguishes "cursor" from "selected" when they differ. */
+  .win7 table > tbody > tr.is-cursor > * {
+    outline: 1px dotted var(--w7-el-c);
+    outline-offset: -1px;
+  }
+
   /* Aero context menu. 7.css has no menu component, so this is hand-authored —
      but ONLY out of the existing --w7-* vars, never literal hex, so the
      hand-written dark Win7 palette above recolours it for free. Values are