sched: guard record_stopped_execution with proven ownership

src/wf_scheduling/poll.py

@@ -432,6 +432,7 @@ class Scheduler:
         boundary, clears the executing mark, and records terminal history.
         Never re-invokes the dispatcher.
         """
+        self._require_ownership()
         from wf_api.run_lifecycle import persist_stopped_run
         from wf_artifacts.runs.models import StoredRunStatus