fix: processor-counts API + ASRX field name conversion

- Fix processor-counts API to correctly read JSON counts:
  - YOLO: use frames.length (was returning null)
  - CUT: prioritize scenes.length over frame_count
  - Result: YOLO 1963 frames, CUT 25 scenes (correct)

- Fix ASRX field name conversion:
  - Convert start_time/end_time → start/end for ASRX compatibility
  - Prefer frame-based positioning over time-based

- Document issues in issues_2026-06-21.md:
  - Issue 6: ASRX field name mismatch
  - Issue 7: processor-counts API null values

scripts/asrx_processor.py

@@ -134,13 +134,24 @@ def _convert_result(result, output_path):
     }
 
     for seg in result.get("segments", []):
-        start_sec = seg["start"]
-        end_sec = seg["end"]
+        # Prefer frame-based (precise positioning)
+        if "start_frame" in seg and "end_frame" in seg:
+            start_frame = seg["start_frame"]
+            end_frame = seg["end_frame"]
+            start_sec = start_frame / fps
+            end_sec = end_frame / fps
+        else:
+            # Fallback to time-based
+            start_sec = seg.get("start", seg.get("start_time", 0))
+            end_sec = seg.get("end", seg.get("end_time", 0))
+            start_frame = int(start_sec * fps)
+            end_frame = int(end_sec * fps)
+        
         output_result["segments"].append({
             "start_time": start_sec,
             "end_time": end_sec,
-            "start_frame": int(start_sec * fps),
-            "end_frame": int(end_sec * fps),
+            "start_frame": start_frame,
+            "end_frame": end_frame,
             "text": seg.get("text", ""),
             "speaker_id": seg.get("speaker_id", seg.get("speaker", "")),
             "language": seg.get("language", ""),