docs: add trace video normal/debug mode to API reference

docs_v1.0/API_V1.0.0/TRACE/TRACE_API_REFERENCE_V1.0.0.md

@@ -179,11 +179,31 @@ height = prev.h + (next.h - prev.h) * t
 
 **`GET /api/v1/file/:file_uuid/trace/:trace_id/video`**
 
-MP4 video with bounding box overlay for a trace.
+MP4 video segment for a face trace. Two modes available:
+
+**Normal mode**: raw video segment, no overlays, stream copy (fastest).
+
+**Debug mode** (default): with bounding box + debug overlay.
 
 | Param | Type | Default | Description |
 |-------|------|---------|-------------|
 | `padding` | float | 2.0 | Padding seconds before/after |
+| `mode` | string | `debug` | `normal` = raw clip, `debug` = with overlay |
+
+**Debug mode overlay info (top-left):**
+```
+Trace: <ID>  Cut: <scene>  <identity_name>
+Frame: <N>  UUID: <file_uuid>
+```
+
+**Usage:**
+```bash
+# Debug mode (default, backward compatible)
+curl -o trace.mp4 "https://host/api/v1/file/{uuid}/trace/{id}/video"
+
+# Normal mode (no overlay, faster)
+curl -o trace.mp4 "https://host/api/v1/file/{uuid}/trace/{id}/video?mode=normal"
+```
 
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