Put every shortcut on one shared keymap and make the app keyboard-reachable

The keymap was scattered over ShortcutsService if-chains, the file panel's
key switch, macOS-only menu accelerators and hand-typed hints in 16
tooltips x 7 locales, and large parts of the app had no keyboard path at
all. src/shared/keymap.ts is now the one table: scopes, per-platform
defaults, exact matching, formatting with localized key names, conflicts,
reserved combos and native-menu accelerators, proven by keymap.spec.ts.

- ShortcutsService resolves against the effective keymap: claim() takes
  the key (preventDefault, held keys repeat only movement, never mid-IME),
  and from a text field only chords and F-keys fire. The file panel, App,
  editor, manager and Settings windows all dispatch through it.
- FileActionsService.run is the one file-command dispatcher for the list
  keys, the row menu, the macOS menu bar and the toolbar.
- New keys: the row menu (Shift+F10 / Menu / Ctrl+Return), the source
  picker (Mod+K), the path bar (Mod+L), transfers (Mod+J), sorting
  (Alt+1-7), Shift+movement selection, close other tabs, move and
  disconnect tabs, refresh and edit on Windows/Linux, permissions, copy
  path, reveal, trash, open in default app, editor find next/previous.
- Right-click menus: soft shortcut hints, icons on the everyday verbs
  (the toolbar's glyphs), section headers, scrolling, item keys while
  open, a highlighted first item when opened from the keyboard. The panel
  source picker now renders through the same menu.
- Dialogs: role=dialog, a Tab trap via cycleFocus (WKWebView skips
  buttons on Tab without Keyboard navigation), initial focus, Esc that
  stops propagating; the chmod dialog takes focus and applies on Enter.
- Fixed: Ctrl+Tab also flipped the active panel; Esc in a manager dialog
  closed the manager; Ctrl-F/T fired Cmd shortcuts on macOS; shortcuts
  fired under dialogs; keys died after any button click on macOS; the
  editor's save prompt and find box never got focus; WebView2 reload keys;
  a window could save default settings before its first load.
- Settings closes on its own close-window key (new settingsClose request).

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

ui/src/app/core/updater.service.ts

@@ -45,6 +45,14 @@ export class UpdaterService {
     void this.rpc.request.applyUpdate({}); // quits + relaunches
   }
 
+  /** The pill's one action, also the "Install update" key: download when
+   *  available, apply (relaunch) once ready; nothing otherwise. */
+  advance(): void {
+    const state = this.state();
+    if (state === 'available') void this.download();
+    else if (state === 'ready') this.apply();
+  }
+
   /** Manual re-check (menu item). */
   async check(): Promise<void> {
     if (!this.rpc.available) return;