feat(terminal): refactor runtime and add mobile workspace (#2280)

Replace the legacy terminal flow with a shared authenticated WebSocket
runtime used across web, desktop, relay, and mobile surfaces.

- introduce the v3 terminal protocol with scoped attachments, snapshots,
  ordered output, bounded replay history, reconnects, and explicit lifecycle
- harden PTY creation, restart, resize, close, force-kill, idle cleanup,
  shell selection, login mode, environment sanitization, and appearance sync
- add runtime-aware terminal APIs with relay authentication and Electron parity
- add a fullscreen mobile terminal workspace with touch scrolling,
  long-press selection, safe-area controls, quick keys, and Ctrl/Alt input
- add terminal selection attachments, preview detection, project actions,
  shell settings, and localized UI
- harden Ghostty rendering, resize recovery, Unicode handling, block
  characters, line height, and stale-row behavior
- remove the obsolete terminal SSE path and update reverse-proxy guidance
- expand terminal runtime, transport, input, selection, and store coverage
- avoid duplicate web builds when preparing mobile assets in root CI builds

packages/ui/src/lib/settings/search.ts

@@ -116,6 +116,14 @@ const SETTINGS_SEARCH_ITEMS: readonly SettingsSearchItem[] = [
     titleKey: 'settings.openchamber.visual.field.terminalFontSize',
     keywords: ['terminal', 'font', 'text size'],
   },
+  {
+    id: 'appearance.terminal-shell',
+    page: 'appearance',
+    titleKey: 'settings.openchamber.visual.field.terminalShell',
+    descriptionKey: 'settings.openchamber.visual.field.terminalShellHint',
+    keywords: ['terminal', 'shell', 'bash', 'zsh', 'fish', 'pwsh', 'powershell'],
+    isAvailable: (ctx) => !ctx.isVSCode,
+  },
   {
     id: 'appearance.editor-font-size',
     page: 'appearance',