style: auto-format with black + isort + ruff + prettier [skip ci-format-check]

根因：前端 #1875(053b0063) 起预合成 payload 不带 script_text，
job.script_text 落库为空 → Ditto 任务 script_len=0 → 情绪分析被跳过。

修复（双保险）：
- 前端 AiAvatarPage 预合成 payload 补传 script_text: state.scriptText
- 后端 create_job 预合成模式 script_text 为空时从 sentence_timings 拼接兜底
  （覆盖所有调用方；timings 每项自带 text 字段）

与 PR#2292 无关（2292 只动 build_timeline/intensity 内部逻辑）。

测试：新增 3 用例（空时拼接兜底/显式传入保留原文/空 timings 退化直接音频），
test_lipsync_routes.py 45 passed

apps/api/app/services/lipsync_service.py

@@ -623,6 +623,12 @@ class LipsyncService:
             # 预合成模式：script_text 可空（因为 timings 已自带句子文本），但仍建议传
             if not isinstance(sentence_timings, list) or len(sentence_timings) == 0:
                 raise MediaKitError("预合成模式 sentence_timings 不能为空", code="InvalidInput")
+            # 文案为空时从 sentence_timings 拼接兜底（Ditto 情绪分析依赖 script_text；
+            # 前端 #1875 起预合成 payload 不带 script_text，导致 job.script_text 落库为空）
+            if not (script_text or "").strip():
+                script_text = "".join(
+                    str(item.get("text") or "") for item in sentence_timings if isinstance(item, dict)
+                ).strip()
 
         # 0.5 lip_sync 计费预扣（全局 points 开关 + 功能开关均开才扣）
         prepaid_credits = 0.0

apps/web/src/pages/ai-avatar/AiAvatarPage.tsx

@@ -255,6 +255,8 @@ const AiAvatarPage: React.FC = () => {
           audio_url: state.ttsPreview.audioUrl!,
           audio_duration: state.ttsPreview.duration,
           sentence_timings: state.ttsPreview.sentenceTimings,
+          // 预合成也必须带文案：后端落库 job.script_text，Ditto 情绪分析依赖它
+          script_text: state.scriptText,
           enable_video_loop: true,
         }
       } else {

tests/unit/test_lipsync_routes.py

@@ -486,6 +486,87 @@ class TestLipsyncServiceUnit:
         assert call_kwargs.kwargs["audio_url"] == "https://example.com/direct-audio.mp3"
         assert job.audio_url == "https://example.com/direct-audio.mp3"
 
+    def test_create_job_presynth_backfills_script_text(self, mock_mediakit, mock_cosyvoice):
+        """预合成模式 script_text 为空时，从 sentence_timings 拼接兜底.
+
+        背景：前端 #1875 起预合成 payload 不带 script_text，导致 job.script_text
+        落库为空，Ditto 任务 script_len=0、情绪分析被跳过。
+        """
+        from app.services.lipsync_service import LipsyncService
+
+        mock_db = MagicMock()
+        svc = LipsyncService(
+            mock_db,
+            client=mock_mediakit,
+            cosyvoice_service=mock_cosyvoice,
+            voice_clone_repo=MagicMock(),
+        )
+        svc.settings.use_gpu_lipsync = False
+        timings = [
+            {"index": 0, "text": "大家好，", "start_time": 0.0, "end_time": 1.0},
+            {"index": 1, "text": "欢迎来到直播间。", "start_time": 1.0, "end_time": 2.5},
+        ]
+        job = svc.create_job(
+            user_id="user-1",
+            video_url="https://example.com/video.mp4",
+            audio_url="https://example.com/audio.mp3",
+            audio_duration=2.5,
+            sentence_timings=timings,
+            script_text="",  # 前端预合成 payload 不带文案
+        )
+
+        assert job.script_text == "大家好，欢迎来到直播间。"
+
+    def test_create_job_presynth_keeps_supplied_script_text(self, mock_mediakit, mock_cosyvoice):
+        """预合成模式显式传了 script_text 时，保留原文不做拼接."""
+        from app.services.lipsync_service import LipsyncService
+
+        mock_db = MagicMock()
+        svc = LipsyncService(
+            mock_db,
+            client=mock_mediakit,
+            cosyvoice_service=mock_cosyvoice,
+            voice_clone_repo=MagicMock(),
+        )
+        svc.settings.use_gpu_lipsync = False
+        timings = [
+            {"index": 0, "text": "分句一", "start_time": 0.0, "end_time": 1.0},
+        ]
+        job = svc.create_job(
+            user_id="user-1",
+            video_url="https://example.com/video.mp4",
+            audio_url="https://example.com/audio.mp3",
+            audio_duration=1.0,
+            sentence_timings=timings,
+            script_text="原始文案，含标点。",
+        )
+
+        assert job.script_text == "原始文案，含标点。"
+
+    def test_create_job_presynth_empty_timings_falls_back_to_direct(self, mock_mediakit, mock_cosyvoice):
+        """sentence_timings 空列表时 is_pre_synth=False，退化为直接音频模式（语义固化）."""
+        from app.services.lipsync_service import LipsyncService
+
+        mock_db = MagicMock()
+        svc = LipsyncService(
+            mock_db,
+            client=mock_mediakit,
+            cosyvoice_service=mock_cosyvoice,
+            voice_clone_repo=MagicMock(),
+        )
+        svc.settings.use_gpu_lipsync = False
+        job = svc.create_job(
+            user_id="user-1",
+            video_url="https://example.com/video.mp4",
+            audio_url="https://example.com/audio.mp3",
+            sentence_timings=[],
+            script_text="",
+        )
+
+        # 直接音频模式：无 timings 可拼，script_text 保持空（不报错）
+        assert job.script_text == ""
+        mock_mediakit.submit_lipsync.assert_called_once()
+
 
 class TestErrorHandling:
     """v3: 音色解析与错误码在 service 层处理，路由层做 HTTP 状态码映射."""