接入原生壳外观查询能力

新增 HostBridge appearance.getColorScheme 只读契约和 H5 facade

Expo 壳通过 React Native Appearance 读取系统配色

Tauri 壳通过主窗口 theme 读取桌面配色

补齐外观查询测试、漂移检查和架构文档

apps/desktop-shell/scripts/check-config.mjs

@@ -133,6 +133,7 @@ const requiredPermissions = [
 const requiredBuildCommands = ['host_bridge_request'];
 const requiredMainSnippets = [
   'tauri_plugin_clipboard_manager::init()',
+  '"appearance.getColorScheme"',
   '"share.open"',
   '"share.setTarget"',
   '"navigation.openNativePage"',
@@ -147,6 +148,7 @@ const requiredMainSnippets = [
   'BASE64_STANDARD.decode',
   'set_title',
   'set_badge_count',
+  'window.theme()',
 ];
 
 for (const permission of requiredPermissions) {