Graceful (force = FALSE, default): creates per-worker stop
files; each worker exits cleanly between jobs once it observes its file.
Slurm jobs end normally; remaining PENDING rows stay in the queue
and can be resumed with another experimentSBATCH call against
the same queue_path.
killExperimentSBATCH(es, force = FALSE, scancel_cmd = "scancel")es, invisibly.
Immediate (force = TRUE): runs scancel <ids> to kill
the Slurm jobs straight away. Any rows that were RUNNING at the
time of cancellation will remain RUNNING in the queue until the
next reclaim pass; clean them up with
tmuxRefreshQueueStatus(es$queue_path).