Turns a received SQS message into a delivery; poison and crash-looping messages are dead-lettered and yield null.
Releases the consumer's independent executor / clients (spec 03 §11).
Throws on a retryable SQS error: the runtime retries on its next heartbeat tick (03 §3.2). Never 'Cancelled'.
Optional_progress: WorkProgressNever returns two deliveries of one partition key for a partitioned subscription (spec 03 §7).
Visibility 0. SQS has already counted this receive; the receive margins (Task 4) absorb it.
CancelInFlight is false on this transport: there is no cancel flag to acknowledge (03 §5).