DriftSweepRow

One drifted cogmap in a sweep result — the map plus its ingest delta since its own watermark.
Ordered most-drifted-first by the sweep (steward_drift_sweep).

{
    "boundary_moved": true,
    "cogmap_id": "b2008c45-9f31-4aae-8f49-0cadcb6ad25e",
    "new_events": 0,
    "new_resources": 0,
    "watermark": "ea4f9af3-b7e1-487b-b9a4-cd5c1b8015d5"
}