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

README.md

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+# Beat Pocket
+
+A browser extension that gives [beat-battle.net](https://beat-battle.net) a
+mobile-first UI without modifying the site itself. We never modify the
+site's code or call its private API — we only restyle the DOM it gives us
+and splice in our own components.
+
+## Status
+
+**V1 in progress.** See [`docs/PLAN.md`](./docs/PLAN.md) for full design.
+
+- [x] Plan
+- [ ] Scaffolding (this commit)
+- [ ] Build via Codex
+- [ ] Smoke-test on Chromium "load unpacked"
+- [ ] Package for Chrome Web Store
+
+## Scope (V1)
+
+| Screen | Treatment |
+|---|---|
+| Home (`/`) | Single-column, big thumb buttons, sticky login chip |
+| Lobby list | Card-per-room, full-width |
+| In-game | Player list → top, score/timer → safe top, action bar → sticky bottom |
+| Chat | NEW: bottom drawer (closed / peeking / expanded) |
+| Profile / Shop / Settings / Events | **Out of scope V1** — link to original site |
+
+Out: voice, native push, anything needing permissions.
+
+## Architecture (TL;DR)
+
+1. **`inject.css`** — mobile overrides for the site's existing CSS variables
+2. **`detector.ts`** — `MutationObserver` watches for `.bb-room-overlay`,
+   route changes
+3. **`layout.ts`** — reflows outer shell, mounts drawer host
+4. **`chat-drawer.ts`** — bottom sheet UI + chat send-bridge
+
+The chat-drawer sends messages by **dispatching synthetic events on the
+site's own chat textarea + button**. The server-side auth, rate limit,
+mute, and profanity filters all stay intact — we don't poke React state.
+
+## Dev (no build step in V1)
+
+```sh
+# Load unpacked extension
+# 1. Open chrome://extensions
+# 2. Toggle Developer Mode
+# 3. "Load unpacked" -> select extension/
+# 4. Visit https://beat-battle.net
+```
+
+For Firefox: `about:debugging#/runtime/this-firefox` → "Load Temporary
+Add-on" → pick `extension/manifest.json`.
+
+## Tech
+
+- Vanilla TypeScript
+- esbuild for the bundle (one-time build, no HMR for V1)
+- MV3 (works in Chromium + Firefox 109+)
+
+## Repo
+
+This project will be pushed to `git.molberg.cloud/bonzi/beat-pocket` once
+the vault session is unlocked.
+
+## License
+
+Private until first public release.