Concat multi-shot source clips and auto-regen match_report.html

1. Cutter-report source clip for multi-segment beats was using only the
   primary in/out, which equals the FIRST segment's range. Beat 10 with
   3 shots therefore showed only ~0.88 s of source instead of all 3.32 s.
   Added extract_concat_clip(): renders each segment as its own MP4 and
   concatenates them via ffmpeg's concat demuxer into one continuous
   source clip the same length as the trailer beat.

   Per-segment intermediate clips (beat_NN_source_seg00.mp4 etc.) are
   kept too so individual shots stay inspectable.

2. _regenerate_cutter_report now also regenerates the legacy
   output/report/match_report.html via src.pipeline.reporter.generate_report.
   Both reports stay in sync after every match command.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

scripts/generate_cutter_report.py

@@ -190,6 +190,62 @@ def extract_clip(video_path: Path, start_s: float, duration_s: float, out: Path)
     return out.exists() and out.stat().st_size > 0
 
 
+def extract_concat_clip(
+    video_path: Path,
+    segments: list[tuple[float, float]],
+    out: Path,
+) -> bool:
+    """Render each (start_s, duration_s) segment then concat into one MP4.
+
+    Used for multi-shot source matches so the cutter sees the assembled
+    source side-by-side with the trailer beat instead of just one segment.
+    """
+    if not video_path.exists() or not segments:
+        return False
+    out.parent.mkdir(parents=True, exist_ok=True)
+    parts: list[Path] = []
+    for idx, (seg_start, seg_dur) in enumerate(segments):
+        part = out.with_name(f"{out.stem}_seg{idx:02d}.mp4")
+        if not extract_clip(video_path, seg_start, seg_dur, part):
+            return False
+        parts.append(part)
+    if not parts:
+        return False
+    # Single segment: just rename / copy.
+    if len(parts) == 1:
+        if parts[0].resolve() != out.resolve():
+            try:
+                if out.exists():
+                    out.unlink()
+                parts[0].rename(out)
+            except OSError:
+                return False
+        return out.exists() and out.stat().st_size > 0
+    # Multi-segment: concat via ffmpeg concat demuxer (codec params match
+    # because every segment is rendered through extract_clip with identical
+    # encoder settings).
+    list_file = out.with_name(f"{out.stem}_concat.txt")
+    list_file.write_text(
+        "\n".join(f"file '{part.as_posix()}'" for part in parts) + "\n",
+        encoding="utf-8",
+    )
+    cmd = [
+        "ffmpeg", "-y", "-loglevel", "error",
+        "-f", "concat", "-safe", "0", "-i", str(list_file),
+        "-c", "copy",
+        "-movflags", "+faststart",
+        str(out),
+    ]
+    try:
+        subprocess.run(cmd, check=True, capture_output=True, timeout=60)
+    finally:
+        try:
+            list_file.unlink()
+        except OSError:
+            pass
+    return out.exists() and out.stat().st_size > 0
+
+
 def beat_still_time(start_s: float, end_s: float) -> float:
     duration = max(0.04, end_s - start_s)
     return start_s + min(0.4, duration * 0.3)
@@ -275,15 +331,32 @@ def collect_rows(
             tmp4 = clips_dir / f"beat_{bid:02d}_trailer.mp4"
             if extract_clip(trailer_path, beat["start_s"], tdur, tmp4):
                 trailer_clip = tmp4
-            # Source clip: full matched duration. May be shorter than the beat
-            # when the match drops out before the beat ends (fade / shot
-            # change in the source); that's intentional — the cutter needs to
-            # see exactly the matched span.
+            # Source clip:
+            #   - segmented match (multi-shot beat): concatenate each
+            #     segment back-to-back so the cutter sees the assembled
+            #     source (e.g. man-shot + reaction shot) at the same total
+            #     length as the trailer beat.
+            #   - single match: extract the full matched span.
+            # May be shorter than the beat when a match drops before the
+            # beat ends (fade / shot change in source) — intentional.
             if rec is not None:
-                sdur = max(0.5, min(CLIP_MAX_DURATION_S, rec["out_point_s"] - rec["in_point_s"]))
+                segs = rec.get("segments") or []
                 smp4 = clips_dir / f"beat_{bid:02d}_source.mp4"
-                if extract_clip(source_path, rec["in_point_s"], sdur, smp4):
-                    source_clip = smp4
+                if len(segs) >= 2:
+                    seg_specs = [
+                        (
+                            float(s["in_point_s"]),
+                            max(0.04, float(s["out_point_s"]) - float(s["in_point_s"])),
+                        )
+                        for s in segs
+                        if float(s["out_point_s"]) > float(s["in_point_s"])
+                    ]
+                    if seg_specs and extract_concat_clip(source_path, seg_specs, smp4):
+                        source_clip = smp4
+                else:
+                    sdur = max(0.5, min(CLIP_MAX_DURATION_S, rec["out_point_s"] - rec["in_point_s"]))
+                    if extract_clip(source_path, rec["in_point_s"], sdur, smp4):
+                        source_clip = smp4
 
         rows.append(BeatRow(
             bid=bid,