feat(app): add textEngine toggle for chat mode (Coze ↔ S2S)

- localStorage-persistent textEngine state ('coze' | 's2s')
- Header button toggles between the two engines when in chat mode
- ChatPanel remounts on engine switch via key=sessionId-textEngine
- Voice mode completely unaffected

test2/client/src/App.jsx

@@ -1,10 +1,11 @@
 import { useState, useEffect, useCallback, useRef } from 'react';
-import { Settings2, Zap, Mic, MessageSquare, History, Plus } from 'lucide-react';
+import { Settings2, Zap, Mic, MessageSquare, History, Plus, Film } from 'lucide-react';
 import VoicePanel from './components/VoicePanel';
 import ChatPanel from './components/ChatPanel';
 import SettingsPanel from './components/SettingsPanel';
 import { getVoiceConfig } from './services/voiceApi';
 import SessionHistoryPanel from './components/SessionHistoryPanel';
+import VideoPanel from './components/VideoPanel';
 
 export default function App() {
   const [showSettings, setShowSettings] = useState(false);
@@ -19,14 +20,25 @@ export default function App() {
   // 文字聊天消息（用于切回语音时注入上下文）
   const [chatMessages, setChatMessages] = useState([]);
   const [settings, setSettings] = useState({
-    botName: '小智',
-    systemRole: '你是一个友善的智能助手，名叫小智。你擅长帮用户解答各类问题。',
-    speakingStyle: '请使用温和、清晰的口吻。',
-    greetingText: '你好，我是你的智能语音助手，有什么可以帮你的吗？',
-    modelVersion: '1.2.1.0',
+    modelVersion: 'O',
     speaker: 'zh_female_vv_jupiter_bigtts',
     enableWebSearch: false,
   });
+  // 文字对话引擎: 'coze' (原方舟 HTTP/SSE) | 's2s' (S2S WebSocket, event 501)
+  const [textEngine, setTextEngine] = useState(() => {
+    try {
+      return localStorage.getItem('bigwo_text_engine') || 'coze';
+    } catch (_) {
+      return 'coze';
+    }
+  });
+  const toggleTextEngine = useCallback(() => {
+    setTextEngine((prev) => {
+      const next = prev === 'coze' ? 's2s' : 'coze';
+      try { localStorage.setItem('bigwo_text_engine', next); } catch (_) {}
+      return next;
+    });
+  }, []);
 
   useEffect(() => {
     getVoiceConfig()
@@ -108,14 +120,18 @@ export default function App() {
             </div>
             <div>
               <h1 className="text-sm font-semibold text-white leading-tight">
-                {mode === 'voice' ? '语音通话' : '文字对话'}
+                {mode === 'voice' ? '语音通话' : mode === 'chat' ? '文字对话' : 'AI 视频'}
               </h1>
               <p className="text-[11px] text-slate-400 leading-tight">
                 {mode === 'voice'
                   ? '直连 S2S 语音 · ChatTTSText'
-                  : handoff?.subtitles?.length > 0
-                    ? '语音转接 · 上下文已延续'
-                    : '方舟 LLM · Function Calling'}
+                  : mode === 'chat'
+                    ? (textEngine === 's2s'
+                      ? 'S2S 文字 · event 501 ChatTextQuery'
+                      : (handoff?.subtitles?.length > 0
+                        ? '语音转接 · 上下文已延续'
+                        : '方舟 LLM · Function Calling'))
+                    : 'Seedance · AI 视频生成'}
               </p>
             </div>
           </div>
@@ -158,7 +174,30 @@ export default function App() {
               >
                 <MessageSquare className="w-3 h-3" /> 文字
               </button>
+              <button
+                onClick={() => setMode('video')}
+                className={`flex items-center gap-1 px-2.5 py-1 rounded-md text-xs transition-all ${
+                  mode === 'video'
+                    ? 'bg-violet-500/20 text-violet-300 font-medium'
+                    : 'text-slate-500 hover:text-slate-300'
+                }`}
+              >
+                <Film className="w-3 h-3" /> 视频
+              </button>
             </div>
+            {mode === 'chat' && (
+              <button
+                onClick={toggleTextEngine}
+                className={`px-2 py-1 rounded-md text-[11px] font-medium transition-colors border ${
+                  textEngine === 's2s'
+                    ? 'bg-emerald-500/15 text-emerald-300 border-emerald-500/30'
+                    : 'bg-slate-700/40 text-slate-300 border-slate-600/40'
+                }`}
+                title="切换文字对话引擎 (S2S 走 event 501, Coze 走 HTTP/SSE)"
+              >
+                {textEngine === 's2s' ? 'S2S' : 'Coze'}
+              </button>
+            )}
             {mode === 'voice' && (
               <button
                 onClick={() => setShowSettings(!showSettings)}
@@ -207,18 +246,23 @@ export default function App() {
               </div>
             </div>
           </>
-        ) : (
+        ) : mode === 'chat' ? (
           /* Chat Panel */
           handoff && (
             <ChatPanel
-              key={handoff.sessionId}
+              key={`${handoff.sessionId}-${textEngine}`}
               sessionId={handoff.sessionId}
               voiceSubtitles={handoff.subtitles}
               settings={settings}
               onBack={handleBackToVoice}
               onMessagesChange={setChatMessages}
+              useS2S={textEngine === 's2s'}
+              playAudioReply={false}
             />
           )
+        ) : (
+          /* Video Panel */
+          <VideoPanel />
         )}
       </main>