Mark the document as extraction-failed.

Constrained transition body for the extraction-failure route. The route loads the row under a per-document advisory lock, verifies the current state is one of the allowed source states, and writes extraction_status="failed" + semantic_index_status="not_required" + a sanitised last_error.layer="extraction". 409 on invalid transitions; idempotent on repeat for already-failed rows.

Constrained-transition acknowledgement. The persisted row is echoed so callers can read back the durable status they just wrote. idempotent: true when the row was already in the failed state and the call only refreshed last_error.