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

extension/manifest.json

@@ -0,0 +1,34 @@
+{
+  "manifest_version": 3,
+  "name": "Beat Pocket",
+  "short_name": "Beat Pocket",
+  "version": "0.1.0",
+  "description": "Mobile-first UI for beat-battle.net. Chat drawer, single-column layout, thumb-sized controls. Uses your existing session — no login required.",
+  "minimum_chrome_version": "109",
+  "icons": {
+    "16": "icons/icon-16.png",
+    "32": "icons/icon-32.png",
+    "48": "icons/icon-48.png",
+    "128": "icons/icon-128.png"
+  },
+  "action": {
+    "default_title": "Beat Pocket",
+    "default_icon": {
+      "16": "icons/icon-16.png",
+      "32": "icons/icon-32.png"
+    }
+  },
+  "background": {
+    "service_worker": "background.js"
+  },
+  "content_scripts": [
+    {
+      "matches": ["*://beat-battle.net/*"],
+      "run_at": "document_idle",
+      "js": ["content/index.js"],
+      "css": ["content/inject.css"]
+    }
+  ],
+  "permissions": ["storage"],
+  "host_permissions": ["*://beat-battle.net/*"]
+}