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/web/server/lib/opencode/settings-runtime.test.js

@@ -39,6 +39,18 @@ const createRuntime = async () => {
 };
 
 describe('settings runtime', () => {
+  it.skipIf(process.platform === 'win32')('writes settings with restrictive directory and file permissions', async () => {
+    const { runtime, settingsFilePath, tempRoot, cleanup } = await createRuntime();
+    try {
+      await runtime.writeSettingsToDisk({ desktopUiPassword: 'secret' });
+
+      expect((await fsPromises.stat(tempRoot)).mode & 0o777).toBe(0o700);
+      expect((await fsPromises.stat(settingsFilePath)).mode & 0o777).toBe(0o600);
+    } finally {
+      await cleanup();
+    }
+  });
+
   it('only remaps project plan paths within the migrated storage directory', async () => {
     const { runtime, settingsFilePath, tempRoot, cleanup } = await createRuntime();
     try {