Fix duplicate cancellation

- Management loop only completes cancelled jobs, doesn't send duplicate cancel messages
- Cancel_job sends the cancel command, management loop cleans up
- Prevents duplicate cancellation logs

vidai/cluster_master.py

@@ -1409,7 +1409,8 @@ class ClusterMaster:
                         cancelled_jobs.append(job_id)
 
                 for job_id in cancelled_jobs:
-                    await self._cancel_job_processing(job_id)
+                    self.complete_job(job_id)
+                    print(f"Completed cancelled job {job_id}")
 
                 await asyncio.sleep(5)  # Poll every 5 seconds