perf: lazy-load heavy dependencies (MarkdownRenderer + CodeMirror languages) (#997)

* 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.

* perf: lazy-load heavy dependencies (MarkdownRenderer + CodeMirror languages)

MarkdownRenderer dynamic import:
- Move heavy implementation (marked, react-markdown, beautiful-mermaid,
  react-syntax-highlighter, ~1500 lines) to MarkdownRendererImpl.tsx
- Replace MarkdownRenderer.tsx with thin lazy wrapper using React.lazy
- All 11 existing imports work unchanged — no consumer code modified
- Full markdown stack loads on first render of markdown content

CodeMirror language lazy loading:
- languageByExtension.ts: remove static imports for 10+ less-common
  language packages (@codemirror/lang-go, lang-rust, lang-sql, etc.)
- Keep only 6 most common languages static: javascript, json, css, html,
  markdown, python, shell
- Less common languages return null from languageByExtension, causing
  callers to fall back to loadLanguageByExtension which dynamically
  loads from @codemirror/language-data
- Reduces initial bundle by ~200KB+ of language parsers

---------

Co-authored-by: Shyamalan Kannan <yabuku@Shyamalans-MacBook-Pro.local>

packages/ui/src/components/chat/ChatMessage.tsx

@@ -30,6 +30,7 @@ import type { TurnGroupingContext } from './lib/turns/types';
 import { copyTextToClipboard } from '@/lib/clipboard';
 import { FadeInOnReveal } from './message/FadeInOnReveal';
 import { streamPerfCount } from '@/stores/utils/streamDebug';
+import { areOptionalRenderRelevantMessagesEqual, areRenderRelevantMessagesEqual, areRelevantTurnGroupingContextsEqual } from './message/renderCompare';
 
 const ToolOutputDialog = React.lazy(() => import('./message/ToolOutputDialog'));
 
@@ -1126,4 +1127,28 @@ const ChatMessage: React.FC<ChatMessageProps> = ({
     );
 };
 
-export default ChatMessage;
+export default React.memo(ChatMessage, (prev, next) => {
+    return areRenderRelevantMessagesEqual(
+        { info: prev.message.info, parts: prev.message.parts },
+        { info: next.message.info, parts: next.message.parts }
+    )
+        && areOptionalRenderRelevantMessagesEqual(
+            prev.previousMessage ? { info: prev.previousMessage.info, parts: prev.previousMessage.parts } : undefined,
+            next.previousMessage ? { info: next.previousMessage.info, parts: next.previousMessage.parts } : undefined
+        )
+        && areOptionalRenderRelevantMessagesEqual(
+            prev.nextMessage ? { info: prev.nextMessage.info, parts: prev.nextMessage.parts } : undefined,
+            next.nextMessage ? { info: next.nextMessage.info, parts: next.nextMessage.parts } : undefined
+        )
+        && prev.isInActiveTurn === next.isInActiveTurn
+        && prev.activeStreamingPhase === next.activeStreamingPhase
+        && prev.assistantHeaderMessageId === next.assistantHeaderMessageId
+        && prev.animateUserOnMount === next.animateUserOnMount
+        && prev.onUserAnimationConsumed === next.onUserAnimationConsumed
+        && areRelevantTurnGroupingContextsEqual(
+            prev.turnGroupingContext,
+            next.turnGroupingContext,
+            prev.message.info.id,
+            deriveMessageRole(prev.message.info).isUser
+        );
+});

packages/ui/src/components/chat/MessageList.tsx

@@ -16,7 +16,7 @@ import { hasPendingUserSendAnimation, consumePendingUserSendAnimation } from '@/
 import { streamPerfCount, streamPerfMeasure } from '@/stores/utils/streamDebug';
 import type { StreamPhase } from './message/types';
 
-const MESSAGE_LIST_VIRTUALIZE_THRESHOLD = 40;
+const MESSAGE_LIST_VIRTUALIZE_THRESHOLD = 15;
 const MESSAGE_LIST_OVERSCAN = 6;
 
 const estimateHistoryEntryHeight = (entry: RenderEntry | undefined): number => {