feat(extension): browser extension for Chrome/Edge/Firefox + CI + v0.8.0

Adds a WXT-based browser extension that replaces manual JS snippet
injection for AI-driven browser testing. The extension auto-connects
to the Muyue server via WebSocket on every page, using the exact
same protocol as the existing snippet — zero backend changes needed.

- Chrome/Edge (MV3) + Firefox (MV2) from single codebase via WXT
- Content script: auto-connect WS, console capture, URL tracking, RPC
- Background service worker: token management, screenshots, badge
- Popup + side panel with server status, sessions, URL config
- CI workflows: build extension, attach .zip to releases
- Makefile targets: ext, ext-chrome, ext-firefox, ext-zip
- Version bumped to 0.8.0

Assisted-by: GLM-5.1 via Crush <crush@charm.land>

extension/README.md

@@ -0,0 +1,81 @@
+# Muyue Browser Extension
+
+AI-powered browser testing & automation, connected to your [Muyue](https://github.com/muyue/muyue) desktop app.
+
+## What it does
+
+- **Auto-injects** the Muyue test client on every page — no more manual snippet copy-paste
+- **Captures console** errors/warnings in real-time, sent to the AI Studio
+- **Enables AI-driven testing**: click buttons, fill inputs, evaluate JS, take screenshots
+- **Side Panel** (Chrome/Edge) and **Sidebar** (Firefox) for status monitoring
+- **Native screenshots** via `chrome.tabs.captureVisibleTab` — pixel-perfect, no SVG hacks
+- **URL change detection** via History API interception (survives SPA navigation)
+- **Badge indicator**: shows connected session count or server status
+
+## Install
+
+### Chrome / Edge
+
+1. Run `npm run build`
+2. Open `chrome://extensions` → Enable **Developer mode**
+3. Click **Load unpacked** → select `extension/.output/chrome-mv3/`
+
+Or install the published extension from the Chrome Web Store.
+
+### Firefox
+
+1. Run `npm run build:firefox`
+2. Open `about:debugging#/runtime/this-firefox`
+3. Click **Load temporary Add-on** → select any file in `extension/.output/firefox-mv2/`
+
+## Development
+
+```bash
+cd extension
+npm install
+npm run dev            # Chrome dev mode with HMR
+npm run dev -- --browser firefox  # Firefox dev mode
+```
+
+## Build
+
+```bash
+npm run build          # Chrome/Edge MV3 → .output/chrome-mv3/
+npm run build:firefox  # Firefox MV2 → .output/firefox-mv2/
+npm run zip            # Chrome .zip for Web Store
+npm run zip:firefox    # Firefox .zip + sources .zip
+```
+
+## Architecture
+
+```
+┌─────────────────────────────────────────────────────┐
+│  Content Script (every HTTP/HTTPS page)              │
+│  - Console interception (log/warn/error)             │
+│  - RPC execution (click, type, eval, list)           │
+│  - URL change detection (History API + MutationObs)  │
+│  - WebSocket → Muyue server (same as snippet)        │
+└──────────────┬──────────────────────────────────────┘
+               │ chrome.runtime messaging
+┌──────────────┴──────────────────────────────────────┐
+│  Background Service Worker                            │
+│  - Token management (GET /api/test/snippet)           │
+│  - Native screenshots (captureVisibleTab)             │
+│  - Badge updates (session count / server status)      │
+│  - chrome.alarms for periodic health checks           │
+└──────────────────────────────────────────────────────┘
+┌──────────────────┐  ┌──────────────────┐
+│  Popup            │  │  Side Panel       │
+│  - Server status  │  │  - Sessions list  │
+│  - Session count  │  │  - Auto-refresh   │
+│  - Dashboard link │  │  - Dashboard link │
+└──────────────────┘  └──────────────────┘
+```
+
+## Compatibility
+
+| Browser | Manifest | Side Panel | Screenshots |
+|---------|----------|------------|-------------|
+| Chrome 89+ | MV3 | ✅ sidePanel API | ✅ captureVisibleTab |
+| Edge 89+ | MV3 | ✅ sidePanel API | ✅ captureVisibleTab |
+| Firefox | MV2 | ✅ sidebar API | ✅ tabs.captureVisibleTab |