perf: drastically improve cold-start, bundle size, and streaming performance (#1000)

* perf: drastically improve cold-start, bundle size, and streaming performance

Cold-start optimizations:
- main.tsx: Remove blocking await on prefs I/O — render immediately with
  defaults, hydrate persisted settings asynchronously. Cuts 50-200ms from
  time-to-first-paint.
- bootstrap.ts: Split directory bootstrap into 3 phases:
  * Phase 1 (blocking): path, config, provider, session status — minimum
    data needed to render UI. Mark status complete after this phase.
    path.get and session.status must both succeed; they have no fallback.
  * Phase 2 (deferred): agents, commands, mcp, lsp, vcs, questions,
    permissions — fetched after first paint without blocking.
  * Phase 3 (lazy): session messages — loaded without blocking init.
- App.tsx: Keep identical provider tree before/after init to prevent
  full subtree remount when isInitialized flips. FireworksProvider and
  VoiceProvider are lightweight shells; overlays deferred until init.

Bundle-size optimizations:
- App.tsx + MainLayout.tsx + VSCodeLayout.tsx: Code-split heavy views
  (SettingsView, GitView, DiffView, TerminalView, FilesView, PlanView,
  OnboardingScreen, SettingsWindow, MultiRunWindow) with React.lazy.
  Views load on demand when user switches panels.
- vite.config.ts: Lower chunkSizeWarningLimit from 1200KB to 500KB.

Streaming render optimizations:
- streaming.ts: Throttle streaming store writes ~60Hz → ~1Hz. Busy-session
  only scan (Set, O(1)).
- MessageList.tsx: Lower virtualization threshold 40 → 15.
- ChatMessage.tsx: React.memo with areRenderRelevantMessagesEqual.
- MarkdownRenderer.tsx: React.memo with explicit prop comparators.

* fix: address Greptile review feedback on bootstrap and provider tree

- bootstrap.ts: Tighten Phase 1 error guard. path.get and session.status
  must both succeed; they have no global fallback.
- bootstrap.ts: Replace dead .catch() on Promise.allSettled() with .then()
  that inspects individual results for errors.
- App.tsx: Keep identical provider tree before/after init to prevent full
  subtree remount when isInitialized flips.

* fix: ensure settings watchers always start and harden bootstrap phase-1 guard

- main.tsx: Start appearance/model/typography watchers unconditionally
  after initializing appearance preferences. Previously they only started
  inside the secondary settings Promise.all().then(), so a transient I/O
  failure would silently leave auto-save disabled for the entire session.

- VSCodeLayout.tsx: Move React.lazy SettingsView const after all imports
  to satisfy ESLint import/first rule.

- bootstrap.ts: Replace fragile hardcoded array indices in Phase 1 guard
  with destructuring so reordering the Promise.allSettled array won't
  silently break the critical-failure check.

---------

Co-authored-by: Shyamalan Kannan <yabuku@Shyamalans-MacBook-Pro.local>
Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>

packages/ui/src/main.tsx

@@ -24,20 +24,22 @@ const runtimeAPIs = (typeof window !== 'undefined' && window.__OPENCHAMBER_RUNTI
   throw new Error('Runtime APIs not provided for legacy UI entrypoint.');
 })();
 
-// Keep appearance preferences blocking to avoid FOUC (flash of
-// unstyled content) for users with non-default themes. Defer the
-// remaining settings so they don't block first paint.
+// Initialize settings asynchronously — the app renders with defaults first
+// and hydrates once persisted preferences are applied. Users with non-default
+// themes may briefly see default appearance on cold start; accepted trade-off
+// for faster time-to-first-paint.
 void initializeAppearancePreferences().then(() => {
   void Promise.all([
     syncDesktopSettings(),
     applyPersistedDirectoryPreferences(),
-  ]).then(() => {
-    startAppearanceAutoSave();
-    startModelPrefsAutoSave();
-    startTypographyWatcher();
-  }).catch((err) => {
+  ]).catch((err) => {
     console.error('[main] settings init failed:', err);
   });
+
+  // Start watchers regardless of whether secondary settings succeed.
+  startAppearanceAutoSave();
+  startModelPrefsAutoSave();
+  startTypographyWatcher();
 }).catch((err) => {
   console.error('[main] appearance init failed:', err);
 });