Integrate JailJS for CSP-restricted execution in browser extension

Major changes:
- Migrate browser-extension to use web-ui package (85% code reduction)
- Add JailJS content script with ES6+ transform support
- Expose DOM constructors (Event, KeyboardEvent, etc.) to JailJS
- Support top-level await by wrapping code in async IIFE
- Add returnFile() support in JailJS execution
- Refactor KeyStore into pluggable storage-adapter pattern
- Make ChatPanel configurable with sandboxUrlProvider and additionalTools
- Update jailjs to 0.1.1

Files deleted (33 duplicate files):
- All browser-extension components, dialogs, state, tools, utils
- Now using web-ui versions via @mariozechner/pi-web-ui

Files added:
- packages/browser-extension/src/content.ts (JailJS content script)
- packages/web-ui/src/state/storage-adapter.ts
- packages/web-ui/src/state/key-store.ts

Browser extension now has only 5 source files (down from 38).

packages/browser-extension/package.json

@@ -15,8 +15,10 @@
     "check": "npm run typecheck"
   },
   "dependencies": {
+    "@mariozechner/jailjs": "^0.1.0",
     "@mariozechner/mini-lit": "^0.1.7",
     "@mariozechner/pi-ai": "^0.5.43",
+    "@mariozechner/pi-web-ui": "^0.5.43",
     "docx-preview": "^0.3.7",
     "js-interpreter": "^6.0.1",
     "jszip": "^3.10.1",