fix: 标题/换行 + TTS replace模式静音原音 + 配音素材库静音原音 (#1504)

Co-authored-by: xiaoxia <dev@xiaoxiajianji.com>
Co-committed-by: xiaoxia <dev@xiaoxiajianji.com>

apps/worker/video_processing/unified_render_service.py

@@ -824,6 +824,17 @@ class UnifiedRenderService:
                 )
                 audio_layer.clips.append(vo_clip)
 
+            # replace 模式：静音原视频音轨（main + broll 图层）
+            if tts_config.overlap_mode == "replace":
+                for layer in layers:
+                    if layer.role in ("main", "broll"):
+                        for clip in layer.clips:
+                            clip.config["volume"] = 0
+                logger.info(
+                    "TTS replace 模式：已静音原视频音轨: plan_id=%s",
+                    self.plan.id,
+                )
+
             logger.info(
                 "TTS 配音已添加: plan_id=%s voice_id=%s segments=%d total_%.2fs",
                 self.plan.id,
@@ -889,6 +900,16 @@ class UnifiedRenderService:
             )
             audio_layer.clips.append(vo_clip)
 
+            # 配音素材库默认替换原音：静音原视频音轨（main + broll 图层）
+            for layer in layers:
+                if layer.role in ("main", "broll"):
+                    for clip in layer.clips:
+                        clip.config["volume"] = 0
+            logger.info(
+                "配音素材库：已静音原视频音轨: plan_id=%s",
+                self.plan.id,
+            )
+
             logger.info(
                 "配音素材库音频已添加到 audio 图层: plan_id=%s duration=%.2fs",
                 self.plan.id,