feat: add cross-browser extension with AI reading assistant

- Create Pi Reader browser extension for Chrome/Firefox
- Chrome uses Side Panel API, Firefox uses Sidebar Action API
- Supports both browsers with separate manifests and unified codebase
- Built with mini-lit components and Tailwind CSS v4
- Features model selection dialog with Ollama support
- Hot reload development server watches both browser builds
- Add useDefineForClassFields: false to fix LitElement reactivity

packages/browser-extension/tsconfig.build.json

@@ -0,0 +1,14 @@
+{
+  "extends": "../../tsconfig.base.json",
+  "compilerOptions": {
+    "rootDir": "./src",
+    "outDir": "./dist",
+    "lib": ["ES2022", "DOM", "DOM.Iterable"],
+    "module": "ESNext",
+    "moduleResolution": "Bundler",
+    "target": "ES2022",
+    "types": ["chrome"]
+  },
+  "include": ["src/**/*.ts"],
+  "exclude": ["dist", "node_modules"]
+}