refactor: merge agent workbench into chat

desktop/src/components/layout/ContentArea.tsx

@@ -1,5 +1,4 @@
 import type { PageKey } from '@/types';
-import { AgentWorkbenchPage } from '@/pages/AgentWorkbenchPage';
 import { ChatPage } from '@/pages/ChatPage';
 import { DrawingPage } from '@/pages/DrawingPage';
 import { KnowledgePage } from '@/pages/KnowledgePage';
@@ -17,8 +16,6 @@ export function ContentArea({ activePage }: ContentAreaProps) {
   switch (activePage) {
     case 'chat':
       return <ChatPage />;
-    case 'agent-workbench':
-      return <AgentWorkbenchPage />;
     case 'drawing':
       return <DrawingPage />;
     case 'knowledge':

desktop/src/components/layout/Sidebar.tsx

@@ -1,6 +1,6 @@
 import { useState } from 'react';
 import { Tooltip, Avatar, theme } from 'antd';
-import { MessageSquare, BookOpen, Brain, Router, FolderOpen, User, Sparkles, ImagePlus, WandSparkles } from 'lucide-react';
+import { MessageSquare, BookOpen, Brain, Router, FolderOpen, User, Sparkles, ImagePlus } from 'lucide-react';
 import { useTranslation } from 'react-i18next';
 import { useUIStore, useSettingsStore } from '@/stores';
 import { useUserProfileStore } from '@/stores/userProfileStore';
@@ -12,7 +12,6 @@ import type { PageKey } from '@/types';
 
 const mainNavItems: { key: PageKey; icon: React.ReactNode; labelKey: string }[] = [
   { key: 'chat', icon: <MessageSquare size={18} />, labelKey: 'nav.chat' },
-  { key: 'agent-workbench', icon: <WandSparkles size={18} />, labelKey: 'nav.agentWorkbench' },
   { key: 'drawing', icon: <ImagePlus size={18} />, labelKey: 'nav.drawing' },
   { key: 'skills', icon: <Sparkles size={18} />, labelKey: 'nav.skills' },
   { key: 'knowledge', icon: <BookOpen size={18} />, labelKey: 'nav.knowledge' },