{
  "fixture": "N03-portable-time-history-merge-r1",
  "duplicate": "A2",
  "conflict": {"record_id": "A3", "decision": "hold_then_resolve", "resolved_seconds": 240},
  "accepted_new": "B1",
  "merged_record_ids": ["A1", "A2", "A3", "B1"],
  "merged_seconds": 900,
  "source_seconds": {"device_a": 720, "device_b": 660}
}