perf: fix streaming lag, memory leaks, stuck spinners, and proxy timeout (#483)

* perf: fix streaming lag, memory leaks, and proxy timeout

- PERF-001: Batch all streaming parts via requestAnimationFrame instead of
  per-token Zustand set() calls (~100/sec → 1 per frame)
- PERF-002: Fix direct state.sessionMemoryState mutation inside set() callback
- PERF-003: Debounce messageStore→sessionStore subscription via rAF + 500ms
  title computation delay
- PERF-004: Stabilize SSE callbacks with refs to prevent reconnection storms;
  add 5-min stuck session idle timeout
- PERF-005: Bound messageCache (500 max, LRU eviction), cap registry Maps,
  cleanup on session eviction
- PERF-006: Replace toast duration: Infinity with 30s + id-based dedup
- Fix proxy timeout: POST /session/:id/message 45s → 4min (matches CLI)
- Add vitest + jsdom test infrastructure (61 tests across 7 files)

Addresses: #476 (stuck spinner), #358 (34GB memory leak), #190 (browser lag)

* perf: virtualize tool output rendering (read, edit, write)

- PERF-007: Replace per-line <SyntaxHighlighter> with VirtualizedCodeBlock:
  - ONE Prism.highlight() call for entire file instead of N per-line calls
  - @tanstack/react-virtual renders only visible rows (~30 vs 2000+)
  - Applied to: ToolPart (read, DiffPreview, WriteInputPreview) and
    ToolOutputDialog (unified diff, read content)
- PERF-008: Memoize parseReadToolOutput/parseDiffToUnified via useMemo
  to prevent re-parsing on every re-render

A 2000-line file read now mounts ~30 DOM nodes instead of 2000
SyntaxHighlighter instances, eliminating the main-thread blocking
that caused UI freezes during file operations.

* fix: resolve lint errors (unused vars in tests and VirtualizedCodeBlock)

* chore: trim PR scope to core perf fixes

* fix: restore tool-card highlight stability

---------

Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>

packages/ui/package.json

@@ -54,6 +54,7 @@
     "@remixicon/react": "^4.7.0",
     "@streamdown/code": "^1.0.2",
     "@streamdown/mermaid": "^1.0.2",
+    "@tanstack/react-virtual": "^3.13.18",
     "@types/react-syntax-highlighter": "^15.5.13",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
@@ -66,6 +67,7 @@
     "http-proxy-middleware": "^3.0.5",
     "motion": "^12.23.24",
     "next-themes": "^0.4.6",
+    "prismjs": "^1.30.0",
     "react": "^19.1.1",
     "react-dom": "^19.1.1",
     "react-syntax-highlighter": "^15.6.6",
@@ -83,6 +85,7 @@
     "@tailwindcss/postcss": "^4.0.0",
     "@tauri-apps/api": "^2.9.0",
     "@types/node": "^24.3.1",
+    "@types/prismjs": "^1.26.6",
     "@types/react": "^19.1.10",
     "@types/react-dom": "^19.1.7",
     "@vitejs/plugin-react": "^5.0.0",