refactor(dashboard): split chat.tsx into modular chat/ directory

- Extract types, utils, and components into separate files
- types.ts: All interfaces and type definitions (107 lines)
- utils.ts: Pure utility functions (50 lines)
- MessageRenderer.tsx: Message rendering components (96 lines)
- VirtualIdentityDialog.tsx: Virtual identity dialog (206 lines)
- ChatTabBar.tsx: Tab bar component (79 lines)
- index.tsx: Main ChatPage component (1147 lines)
- Update router import path to chat/index
- Fix TypeScript type imports per verbatimModuleSyntax
- Build passes with zero errors

dashboard/src/routes/chat/ChatTabBar.tsx

@@ -0,0 +1,79 @@
+import { cn } from '@/lib/utils'
+import { MessageSquare, Plus, UserCircle2, X } from 'lucide-react'
+
+import type { ChatTab } from './types'
+
+interface ChatTabBarProps {
+  tabs: ChatTab[]
+  activeTabId: string
+  onSwitch: (tabId: string) => void
+  onClose: (tabId: string, e?: React.MouseEvent) => void
+  onAddVirtual: () => void
+}
+
+export function ChatTabBar({
+  tabs,
+  activeTabId,
+  onSwitch,
+  onClose,
+  onAddVirtual,
+}: ChatTabBarProps) {
+  return (
+    <div className="shrink-0 border-b bg-muted/30">
+      <div className="max-w-4xl mx-auto px-2 sm:px-4">
+        <div className="flex items-center gap-1 overflow-x-auto py-1.5 scrollbar-thin">
+          {tabs.map((tab) => (
+            <div
+              key={tab.id}
+              className={cn(
+                "flex items-center gap-1.5 px-3 py-1.5 rounded-md text-sm whitespace-nowrap transition-colors cursor-pointer",
+                "hover:bg-muted",
+                activeTabId === tab.id
+                  ? "bg-background shadow-sm border"
+                  : "text-muted-foreground"
+              )}
+              onClick={() => onSwitch(tab.id)}
+            >
+              {tab.type === 'webui' ? (
+                <MessageSquare className="h-3.5 w-3.5" />
+              ) : (
+                <UserCircle2 className="h-3.5 w-3.5" />
+              )}
+              <span className="max-w-[100px] truncate">{tab.label}</span>
+              {/* 连接状态指示器 */}
+              <span className={cn(
+                "w-1.5 h-1.5 rounded-full",
+                tab.isConnected ? "bg-green-500" : "bg-muted-foreground/50"
+              )} />
+              {/* 关闭按钮（非默认标签页） */}
+              {tab.id !== 'webui-default' && (
+                <span
+                  onClick={(e) => onClose(tab.id, e)}
+                  className="ml-0.5 p-0.5 rounded hover:bg-muted-foreground/20 cursor-pointer"
+                  role="button"
+                  tabIndex={0}
+                  onKeyDown={(e) => {
+                    if (e.key === 'Enter' || e.key === ' ') {
+                      e.preventDefault()
+                      onClose(tab.id, e as any)
+                    }
+                  }}
+                >
+                  <X className="h-3 w-3" />
+                </span>
+              )}
+            </div>
+          ))}
+          {/* 新建虚拟身份标签页按钮 */}
+          <button
+            onClick={onAddVirtual}
+            className="flex items-center gap-1 px-2 py-1.5 rounded-md text-sm text-muted-foreground hover:bg-muted hover:text-foreground transition-colors"
+            title="新建虚拟身份对话"
+          >
+            <Plus className="h-3.5 w-3.5" />
+          </button>
+        </div>
+      </div>
+    </div>
+  )
+}