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/stores/useFilesViewTabsStore.test.ts

@@ -3,7 +3,7 @@ import { useFilesViewTabsStore } from './useFilesViewTabsStore';
 
 describe('useFilesViewTabsStore', () => {
   beforeEach(() => {
-    useFilesViewTabsStore.setState({ byRoot: {} });
+    useFilesViewTabsStore.setState({ byRoot: {}, activeRuntimeKey: 'runtime-a', runtimeSnapshots: {} });
   });
 
   test('ignores runtime paths outside the requested root', () => {
@@ -47,4 +47,16 @@ describe('useFilesViewTabsStore', () => {
     expect(state?.openPaths).toEqual(['/repo/src/index.ts']);
     expect(state?.expandedPaths).toEqual(['/repo/src', '/repo/other']);
   });
+
+  test('restores independent active projections across runtime switches', () => {
+    useFilesViewTabsStore.getState().addOpenPath('/repo', '/repo/a.ts');
+    useFilesViewTabsStore.getState().resetForRuntimeSwitch('runtime-b');
+    expect(useFilesViewTabsStore.getState().byRoot).toEqual({});
+    useFilesViewTabsStore.getState().addOpenPath('/repo', '/repo/b.ts');
+
+    useFilesViewTabsStore.getState().resetForRuntimeSwitch('runtime-a');
+    expect(useFilesViewTabsStore.getState().byRoot['/repo']?.openPaths).toEqual(['/repo/a.ts']);
+    useFilesViewTabsStore.getState().resetForRuntimeSwitch('runtime-b');
+    expect(useFilesViewTabsStore.getState().byRoot['/repo']?.openPaths).toEqual(['/repo/b.ts']);
+  });
 });