feat(mobile): mobile app navigation rework and beta-feedback closeout (#2561)

Navigation model rebuilt around two full-width drawers and a minimal
header (sessions / title-switcher / usage ring / workspace):

- Left sessions drawer: cross-project tree with live status indicators,
  swipe actions on sessions (rename/archive/delete) and on group headers
  (project edit / two-step close, worktree delete), reorder-only edit
  mode with collapsible project cards and draggable worktrees, app-level
  footer (connected instance, settings, pending web update).
- Right workspace drawer: Changes / Files / Terminal / Notes / MCP as
  pill tabs (inactive tabs icon-only); panes stay mounted once visited.
  The full desktop file editor serves the Files tab; read/skill tool taps
  in chat open the file there at the requested line.
- Header session switcher on title tap: 10 cross-project recents with
  live busy/attention indicators and project · branch metadata; the
  usage ring opens a metadata overlay with an explicit loading state.
- The overflow menu is gone on phones (its destinations moved into the
  drawers); iPad keeps it until its dedicated layout pass.

Correctness and continuity:

- /auth/session answers bearer-first, so a stale WebView cookie can no
  longer mask a revoked device token; cold launches classify failures
  fast and land on an explicit connect screen.
- Authoritative session snapshots raise frozen ordering baselines and
  stale live ranks — recents stay truthful after the app slept.
- Cold launches reopen the last active session per instance (persisted
  pointer, confirmed against a sessions snapshot; a user-opened draft
  clears it), with a logo hold instead of a draft flash.

Also: collapsed pill composer gains the stop control; chat tool rows
share one 36px rhythm; Task subtool rows truncate; larger bottom safe
area so the composer clears big-screen corner radii; Capacitor build
hides About/Update (store updates apply there); widgets link to the
sessions drawer with a list icon; MobileApp split into focused modules;
five mobile-surface detectors unified; translucent borders normalized to
70%; all new strings translated across the 10 locales.

iPad and foldable layouts are intentionally untouched - separate next version PR.

packages/ui/src/lib/runtimeSurface.ts

@@ -1,4 +1,6 @@
-import { isDesktopShell } from '@/lib/desktop';
+import { isDesktopShell, isVSCodeRuntime } from '@/lib/desktop';
+import { isCapacitorApp } from '@/lib/platform';
+import { getStoredMobileLayoutPreference } from '@/lib/mobileLayoutPreference';
 
 export type HostedSurface = 'desktop' | 'mobile';
 
@@ -20,7 +22,14 @@ const isTouchOrCoarsePointer = (): boolean => {
   return coarsePointer || touchPoints > 0;
 };
 
-const detectHostedSurface = (): HostedSurface => {
+/**
+ * Single authority for the mobile-vs-desktop surface decision.
+ *
+ * Priority: explicit stamp (set once at boot) → URL override → Capacitor
+ * shell (always the mobile surface) → desktop shells → phone heuristic
+ * gated by the stored mobile layout preference.
+ */
+export const detectHostedSurface = (): HostedSurface => {
   if (typeof window === 'undefined') return 'desktop';
 
   const explicitSurface = window.__OPENCHAMBER_SURFACE__;
@@ -33,12 +42,30 @@ const detectHostedSurface = (): HostedSurface => {
     return override;
   }
 
-  if (isDesktopShell()) return 'desktop';
+  if (isCapacitorApp()) return 'mobile';
+  if (isDesktopShell() || isVSCodeRuntime()) return 'desktop';
 
-  const width = window.innerWidth || window.screen?.width || 0;
-  return width > 0 && width <= MOBILE_SURFACE_MAX_WIDTH && isTouchOrCoarsePointer()
-    ? 'mobile'
-    : 'desktop';
+  const width = Math.min(
+    window.innerWidth || Number.POSITIVE_INFINITY,
+    window.screen?.width || Number.POSITIVE_INFINITY,
+  );
+  const likelyPhone = Number.isFinite(width)
+    && width <= MOBILE_SURFACE_MAX_WIDTH
+    && isTouchOrCoarsePointer();
+  return likelyPhone && getStoredMobileLayoutPreference() === 'new' ? 'mobile' : 'desktop';
+};
+
+/**
+ * Decides the surface once and stamps it on `window` so every later
+ * `isMobileSurfaceRuntime()` call (perf tuning, sync paging, device info)
+ * reads the same stable answer instead of re-running viewport heuristics.
+ */
+export const resolveHostedSurface = (): HostedSurface => {
+  const surface = detectHostedSurface();
+  if (typeof window !== 'undefined') {
+    window.__OPENCHAMBER_SURFACE__ = surface;
+  }
+  return surface;
 };
 
 export const isMobileSurfaceRuntime = (): boolean => detectHostedSurface() === 'mobile';