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/web-ui/src/state/transports/DirectTransport.ts

@@ -1,5 +1,5 @@
 import { type AgentContext, agentLoop, type Message, type PromptConfig, type UserMessage } from "@mariozechner/pi-ai";
-import { keyStore } from "../KeyStore.js";
+import { getKeyStore } from "../key-store.js";
 import type { AgentRunConfig, AgentTransport } from "./types.js";
 
 export class DirectTransport implements AgentTransport {
@@ -7,7 +7,7 @@ export class DirectTransport implements AgentTransport {
 
 	async *run(userMessage: Message, cfg: AgentRunConfig, signal?: AbortSignal) {
 		// Get API key from KeyStore
-		const apiKey = await keyStore.getKey(cfg.model.provider);
+		const apiKey = await getKeyStore().getKey(cfg.model.provider);
 		if (!apiKey) {
 			throw new Error("no-api-key");
 		}