fix(butler): wire verification gaps — pain storage init, cold start, UI mode switches

- Call init_pain_storage() in Tauri .setup() so pain persistence activates on boot
- Integrate useColdStart hook into FirstConversationPrompt for auto-greeting
- Add UI mode toggle section to Settings/General (already had imports)
- Add "简洁" mode switch-back button to TopBar in professional layout
- Update SemanticSkillRouter @reserved annotation to reflect active status

desktop/src/components/TopBar.tsx

@@ -1,5 +1,6 @@
-import { ClipboardList } from 'lucide-react';
+import { ClipboardList, Minimize2 } from 'lucide-react';
 import { Button } from './ui';
+import { useUIModeStore } from '../store/uiModeStore';
 
 interface TopBarProps {
   title: string;
@@ -32,6 +33,17 @@ export function TopBar({
 
       {/* 右侧按钮 */}
       <div className="flex items-center gap-1">
+        {/* 切换简洁模式 */}
+        <Button
+          variant="ghost"
+          size="sm"
+          onClick={() => useUIModeStore.getState().setMode('simple')}
+          className="flex items-center gap-2 text-gray-600 dark:text-gray-400 hover:text-gray-900 dark:hover:text-gray-100"
+          title="切换到简洁模式"
+        >
+          <Minimize2 className="w-4 h-4" />
+          <span className="text-sm">简洁</span>
+        </Button>
         {/* 详情按钮 */}
         {showDetailButton && onOpenDetail && (
           <Button