Initial scaffold: Beat Pocket MV3 extension

- manifest.json with MV3 config, host permissions for beat-battle.net
- content/detector.ts: route + overlay observer, emits bbp:phase events
- content/layout.ts: defensive mobile-first layout reflow
- content/chat-drawer.ts: bottom-sheet drawer, dispatches synthetic events
  through site's own React-managed textarea + button (preserves auth,
  rate-limit, mute, profanity guards)
- content/util/selectors.ts: text- and role-based fallback chain
- content/util/ws-proxy.ts: lightweight WebSocket instrumentation, no
  payload capture
- content/inject.css: mobile overrides using site's existing --bb-* vars
- background.js: MV3 service worker stub
- package.json + tsconfig.json + esbuild.config.mjs: build pipeline
- icons/: 16/32/48/128 placeholder PNGs (chili-red disc)
- docs/PLAN.md: full V1 architecture, risks, scope
- README.md: scope, dev workflow (load unpacked), tech

package.json

@@ -0,0 +1,16 @@
+{
+  "name": "beat-pocket",
+  "version": "0.1.0",
+  "private": true,
+  "description": "Mobile-first browser extension for beat-battle.net",
+  "scripts": {
+    "build": "node esbuild.config.mjs",
+    "watch": "node esbuild.config.mjs --watch",
+    "typecheck": "tsc --noEmit"
+  },
+  "devDependencies": {
+    "@types/chrome": "^0.0.270",
+    "esbuild": "^0.21.0",
+    "typescript": "^5.4.0"
+  }
+}