feat: preserve multi-track audio in clip extraction

SKILL.md:
- Step 6: two clip modes — video-only (frame extraction) vs all-streams (editor use)
- Pitfall #10: warn about dropping audio tracks with default -map 0:v:0
- Note on keyframe accuracy vs frame-exact re-encode

extract_frames.py:
- New --all-streams flag on clip subcommand
- -map 0 preserves video + all audio tracks + subtitles
- Default remains -map 0:v:0 for fast frame extraction

SKILL.md

@@ -171,10 +171,22 @@ uv run --directory SKILL_DIR python scripts/index/manage_index.py check-range --
 
 **Clip extraction** (keyframe-accurate, `-c copy`):
 
+For frame extraction purposes, only the video stream is needed:
+
 ```bash
 ffmpeg -hide_banner -y -ss START -to END -i VIDEO_PATH -c copy -map 0:v:0 CLIP_PATH
 ```
 
+For clips that the user may want to import into a video editor or play back, **preserve all audio tracks** by mapping all streams instead of only the video:
+
+```bash
+ffmpeg -hide_banner -y -ss START -to END -i VIDEO_PATH -c copy -map 0 CLIP_PATH
+```
+
+`-map 0` copies all streams (video + all audio tracks + subtitles). The agent should ask the user whether they need a full-multitrack clip or a video-only clip for frame extraction. When in doubt, produce both: a video-only clip for fast frame extraction, and a full-multitrack clip if the user plans to use it in an editor.
+
+**Note:** When using `-c copy` with `-ss` before `-i`, seek accuracy is keyframe-level. If the user needs frame-exact cuts, re-encode is required (significantly slower). Keyframe accuracy is sufficient for planning purposes.
+
 **Frame extraction** (scene detection + uniform sampling, hardware-accelerated, downsampled):
 
 ```bash
@@ -315,6 +327,7 @@ This creates an isolated venv with `funasr`, `torch`, `torchaudio`. If the user
 7. **Mixing funasr-script flags.** The bundled `funasr-nano`/`funasr-fast` use `--track STREAM_INDEX` and `--output-dir DIR`. Do not use the legacy `~/.local/bin/funasr-transcribe` wrapper's flags.
 8. **Hardcoding tool names.** This skill is agent-agnostic. Do not assume specific MCP tools or APIs exist. Use whatever the runtime provides for vision analysis, background execution, and user notification.
 9. **Hardcoding output language.** The edit plan table and all user-facing text must follow the user's language, not a fixed language. The English table in Step 8 is a template — translate columns and content to match the user's language at runtime.
+10. **Dropping audio tracks during clip extraction.** The default clip command maps only `0:v:0` (video-only) for fast frame extraction. If the user plans to import the clip into a video editor, use `--all-streams` (or `-map 0`) to preserve all audio tracks. Always ask the user which they need.
 
 ## Verification checklist
 

scripts/frames/extract_frames.py

@@ -65,13 +65,19 @@ def cmd_clip(args: argparse.Namespace) -> None:
     if not video.exists():
         sys.exit(f"Video not found: {video}")
 
+    # Build stream mapping: video-only for frame extraction, or all streams for editor use
+    if args.all_streams:
+        stream_map = ["-map", "0"]  # all streams (video + all audio + subtitles)
+    else:
+        stream_map = ["-map", "0:v:0"]  # video only (faster, smaller for frame extraction)
+
     cmd = [
         "ffmpeg", "-hide_banner", "-y",
         "-ss", str(args.start),
         "-to", str(args.end),
         "-i", str(video),
         "-c", "copy",
-        "-map", "0:v:0",
+        *stream_map,
         str(output),
     ]
 
@@ -192,6 +198,8 @@ def main() -> None:
     p_clip.add_argument("--start", required=True, type=float, help="Start time in seconds")
     p_clip.add_argument("--end", required=True, type=float, help="End time in seconds")
     p_clip.add_argument("--output", required=True, help="Output clip path")
+    p_clip.add_argument("--all-streams", action="store_true", default=False,
+                        help="Preserve all streams (video + all audio tracks + subtitles). Default: video only (for frame extraction)")
 
     # frames
     p_frames = sub.add_parser("frames", help="Extract frames from a video/clip")