feat(extension): Chrome/Edge only + side panel chat tabs (v0.9.0)

- Remove Firefox build support (CI, Makefile, wxt config)
- Fix chrome.alarms undefined error (add 'alarms' permission)
- Add Chat tab to side panel connected to Studio API (/api/chat)
- Streaming SSE, tool calls, code blocks, thinking display
- Shared chat history with desktop Studio
- New lib/api.js client for extension chat endpoints

💘 Generated with Crush

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

extension/package.json

@@ -1,14 +1,12 @@
 {
   "name": "muyue-extension",
-  "version": "0.8.0",
+  "version": "0.9.0",
   "private": true,
   "type": "module",
   "scripts": {
     "dev": "wxt",
     "build": "wxt build",
-    "build:firefox": "wxt build --browser firefox",
-    "zip": "wxt zip",
-    "zip:firefox": "wxt zip --browser firefox"
+    "zip": "wxt zip"
   },
   "dependencies": {
     "wxt": "^0.20"