fix(conversation): 修复实时会话 TTS/回复被离屏 WS 抢占

- 列表预热仅预取消息缓存，避免后台 WebSocket 覆盖服务端连接
- RealtimeSession UI 回调按 owner 独占，防止 offscreen 覆盖聊天页
- 列表页聚焦时再 prewarm，会话页 TTS 入队优先 base64
- 管线下发 TTS 同时带 audio_base64 与 audio_url；协议说明同步
- 移除 TTS 排查用前后端调试日志，保留错误/告警
- 补充 WS / RealtimeSession / entry-warmup / 播放器相关单测

Co-authored-by: Cursor <cursoragent@cursor.com>

app-expo/tests/features/conversation/entry-warmup.test.ts

@@ -1,6 +1,7 @@
 import { QueryClient } from '@tanstack/react-query';
 
 import {
+  prewarmConversationSession,
   prefetchConversationMessages,
   warmupConversationOpening,
 } from '@/features/conversation/entry-warmup';
@@ -90,6 +91,20 @@ describe('conversation entry warmup', () => {
     ).resolves.toBeUndefined();
   });
 
+  test('prewarms existing conversations without opening an offscreen websocket', async () => {
+    const existing = assistantMessage();
+    mockLoadMessages.mockResolvedValueOnce([existing]);
+
+    prewarmConversationSession(queryClient, 'conv-1');
+    await new Promise((r) => setImmediate(r));
+
+    expect(mockLoadMessages).toHaveBeenCalledWith('conv-1');
+    expect(mockSessions).toHaveLength(0);
+    expect(
+      queryClient.getQueryData(conversationKeys.messages('conv-1')),
+    ).toEqual([existing]);
+  });
+
   test('uses refreshed history and skips websocket when opening is already cached', async () => {
     const existing = assistantMessage();
     mockLoadMessages.mockResolvedValueOnce([existing]);