Cancel Selected V1

Cancel a caller-selected set of runs of any kind in one call.

Every id is ownership-checked BEFORE anything is cancelled — a cross-user or missing id fails the whole call with 404 resource_missing and no existence leak, exactly like run-selected. Rows that cannot be cancelled are skipped with a reason rather than failing the batch: terminal rows, drafts (delete those instead) and running single-points (they finish in seconds). Queued rows are cancelled immediately with a full refund. A running sweep or dynamic run gets a durable cancel request the worker honours at its next point or integration chunk boundary, so it comes back under requested: the run stays running, keeps the results it has already produced, and turns canceled with a partial result and a full refund when the worker stops.