perf: overhaul session loading, caching, and runtime isolation (#2360)

Improve OpenChamber responsiveness under large session workloads while fixing
cache, synchronization, and persistence correctness across runtimes, projects,
directories, and worktrees.

- prioritize selected and visible sessions during bootstrap and defer
  non-critical enrichment work
- reduce redundant message loading, event processing, store publication, and
  hidden sidebar work
- prevent stale session and message requests from overwriting newer
  authoritative state
- preserve existing data when authoritative fetches fail instead of treating
  failures as successful empty responses
- scope session materialization, messages, drafts, queues, todos, pins,
  permissions, folders, tabs, Git state, and pull request data by runtime and
  directory identity
- harden runtime switching, reconnect, cleanup, mutation reconciliation, and
  persisted-state ordering
- preserve live subagent Task linkage when metadata arrives after an older
  message request or while streaming parts are suspended
- coalesce overlapping tail refreshes without losing newer refresh demand
- improve cold-session loading by moving deferrable work out of the critical
  bootstrap path
- isolate URL authentication, mobile credentials, native secrets, and other
  runtime-owned state across endpoint changes
- bound long-lived caches and remove avoidable allocations from event and
  rendering hot paths
- limit virtualization to archive collections where it improves rendering
  without disrupting active sidebar layout
- stabilize session folders, pin ordering, expanded state, and persisted
  sidebar behavior
- open skill files through the same secure editor and outside-workspace grant
  flow used by file navigation, including worktree sessions
- expand regression coverage for stale completions, runtime collisions,
  reconnect behavior, persistence races, authoritative empty results, and
  subagent refresh ordering
- document the updated synchronization, cache ownership, performance, and
  runtime-isolation invariants

packages/ui/src/components/layout/__tests__/mainLayoutMobileSidebarMount.test.ts

@@ -8,6 +8,10 @@ const mainLayoutSource = readFileSync(
     join(__dirname, '..', 'MainLayout.tsx'),
     'utf-8',
 );
+const sessionSidebarSource = readFileSync(
+    join(__dirname, '..', '..', 'session', 'SessionSidebar.tsx'),
+    'utf-8',
+);
 
 describe('MainLayout mobile SessionSidebar mount (issue #1695 regression guard)', () => {
     test('mobile SessionSidebar is not conditionally mounted on mobileLeftDrawerVisible', () => {
@@ -20,10 +24,11 @@ describe('MainLayout mobile SessionSidebar mount (issue #1695 regression guard)'
         expect(/\{\s*mobileLeftDrawerVisible\s*&&\s*\(/.test(precedingWindow)).toBe(false);
 
         expect(precedingWindow.includes('pointer-events-none')).toBe(true);
+        expect(mainLayoutSource.slice(mobileSidebarIndex, mobileSidebarIndex + 120)).toContain('isVisible={mobileLeftDrawerVisible}');
     });
 
     test('desktop SessionSidebar is rendered inside Sidebar without drawer-visibility gating', () => {
-        const desktopSidebarIndex = mainLayoutSource.indexOf('<SessionSidebar />');
+        const desktopSidebarIndex = mainLayoutSource.indexOf('<SessionSidebar isVisible={isSidebarOpen} />');
         expect(desktopSidebarIndex).toBeGreaterThan(-1);
 
         const windowStart = Math.max(0, desktopSidebarIndex - 300);
@@ -32,4 +37,12 @@ describe('MainLayout mobile SessionSidebar mount (issue #1695 regression guard)'
         expect(precedingWindow).toContain('<Sidebar');
         expect(/mobileLeftDrawerVisible\s*&&/.test(precedingWindow)).toBe(false);
     });
+
+    test('hidden sidebars disable render-only subscriptions and effects', () => {
+        expect(sessionSidebarSource).toContain('useGitAllBranches(isVisible)');
+        expect(sessionSidebarSource).toContain('useGitRepoStatusMap(isVisible ? normalizedProjectPaths : EMPTY_STRING_ARRAY)');
+        expect(sessionSidebarSource).toContain('enabled: isVisible,\n    isSessionSearchOpen');
+        expect(sessionSidebarSource).toContain('enabled: isVisible,\n    isDesktopShellRuntime');
+        expect(sessionSidebarSource).toContain('if (!isVisible) return EMPTY_STRING_ARRAY;');
+    });
 });