perf: reduce extension startup work

[tiye]

Summary

• enable Vite/Oxc production minification, reducing eager side-panel JavaScript from about 1.35 MB to 693 KB
• package the existing Gemini icon locally and remove startup requests for the remote favicon and unused web-app manifest
• replace the <all_urls> static content script with on-demand activeTab script execution for selection reads and text insertion
• return null on restricted/unavailable tabs instead of leaving selection requests pending
• update CI to enforce the optimized extension manifest and package shape

摘要

• 启用 Vite/Oxc 生产压缩，将侧边栏首屏 eager JavaScript 从约 1.35 MB 降至 693 KB
• 将现有 Gemini 图标打包为本地资源，移除远程 favicon 与未使用 Web App Manifest 的启动请求
• 移除 <all_urls> 静态 content script，改用 activeTab 在读取选区和填写文本时按需执行脚本
• 受限或不可用页面返回 null，避免选区请求一直 pending
• 更新 CI，持续检查优化后的 Manifest 与扩展包结构

Validation

• JavaScript syntax checks for service worker and side-panel bridge
• Manifest JSON and permission assertions
• Vite 8.2.2/Oxc production build
• packaged output contains a local favicon and no startup remote URL
• eager JavaScript comparison: 1,346,010 -> 693,071 bytes
• GitHub Actions on ubuntu-latest: passed