Get Harbor Action Execution

Read a metadata-only action receipt without resubmitting the action. Use a currently valid scoped credential belonging to the original Harbor. The receipt remains readable after the action or rollout feature is disabled. A credential from another Harbor cannot inspect it. The response does not contain lookup values, input values, output payloads, credential secrets, or raw provider errors. It includes structured operation identity, lookup field names, submitted field names, and the original credential ID. An overdue executing receipt transitions atomically to `unknown`; this read never invokes the destination provider. Stop polling at `succeeded`, `failed`, or `unknown`. Unknown is terminal for this execution identifier and means the update may have happened. Investigate rather than preparing a replacement action to retry. Preparation alone has no execution receipt. A `404 Not Found` after an uncertain execution does not prove the operation never happened. Send a new nonzero UUID in `X-Polytomic-Activity-Request-ID`. Direct REST requests may omit `X-Polytomic-Harbor-Session`; a supplied session must be active and bound to the same credential and Harbor.