perf(diff): Pierre diff optimizations (#419)

* perf: implement virtualized rendering for diff viewer

- Enables efficient rendering of large diffs by only rendering visible content
- Uses shared virtualizer cache to optimize memory across multiple diff viewers
- Configures virtual scrolling with 24px line height for consistent layout

* fix: improve diff viewer line selection and annotation rendering

* fix: normalize line ranges to prevent selection bugs

* chore: upgrade @opencode-ai/sdk to v1.1.65

packages/vscode/package.json

@@ -229,7 +229,7 @@
   },
   "dependencies": {
     "@openchamber/ui": "workspace:*",
-    "@opencode-ai/sdk": "^1.1.53",
+    "@opencode-ai/sdk": "^1.1.65",
     "adm-zip": "^0.5.16",
     "jsonc-parser": "^3.3.1",
     "react": "^19.1.1",