Pane focus reads from band strength, not from the dots; cursor visible in both panes

The previous model made the dotted rectangle the de-facto focus signal: the
cursor row got ONLY dots (and only in the active pane), so an unfocused pane's
cursor row disappeared entirely, and selection strength was the only band
difference. Wrong way around for a commander UI.

Now (matching Win7 Explorer / the commander convention):
- tr.highlighted = "selected via Space" OR "cursor row" — the template ORs
  them, so the cursor row always carries the selection band in BOTH panes.
- Pane focus is what changes the band: strong Aero band (--w7-el-grad-h) in
  the focused pane, 7.css's own faint inactive wash in the unfocused pane —
  that wash IS Win7's inactive-selection colour, faint by design.
- The dotted rect is demoted to what it was in Win7: a keyboard-focus marker
  layered ON TOP of the band, focused pane only. It is no longer the thing
  that tells you which pane is active.

Harness now renders a focused and an unfocused pane stacked, with selected
rows and a cursor row in each; verified zoomed in light and dark.

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

ui/src/app/file-panel/file-panel.html

@@ -279,7 +279,7 @@
           (click)="rowClick($event, i)"
           (dblclick)="openAt(i)"
           (contextmenu)="rowContextMenu($event, i)"
-          [class.highlighted]="isSelected(entry)"
+          [class.highlighted]="isSelected(entry) || i === panel().cursor()"
           [class.is-cursor]="i === panel().cursor() && isActive()"
         >
           <td>