Mobile Bridge v0.2.1

中文\n\n- 移除 Mobile Bridge 对 Harness 页面注入的泛化窄屏 CSS；各 Harness 功能包继续拥有自己的响应式界面。\n- Host 在滚动升级期间保留空的兼容样式路由；0.2.1 relay 不再注入该样式链接。\n- Pixel 7 系统测试覆盖首次使用、全屏设置、目录操作、双设备配对和定向下线。\n- 根 README 改为中英双语，并把双语同步写入贡献规则。\n\n## English\n\n- Stops Mobile Bridge from injecting broad narrow-screen CSS into Harness pages; each Harness package retains ownership of its responsive UI.\n- Keeps an empty Host compatibility stylesheet during rolling upgrades; the 0.2.1 relay no longer injects the stylesheet link.\n- Extends Pixel 7 system coverage across first use, full-screen Settings, directory actions, two-device pairing, and targeted revoke.\n- Makes the root README bilingual and codifies synchronized Chinese/English documentation.\n