Benchmark batches on a shared host: make the runner stoppable between takes and resumable by subset

If another user can claim an exclusive window on your benchmark host at short notice, three things make the handover clean. (1) Know where each take is: take N's driver may be in a pre-launch phase, e.g. a 60 s 'is the host free' gate sleep. Stopping it there is clean, with nothing launched and no partial measurement, so check that before you kill. (2) Stop in the right order: first the local loop, so it can't start take N+1, then the remote process group by its recorded pgid. Verify 0 processes are left, and verify that no app or display server of yours is still running. (3) Mark a stopped take void (rename its folder) rather than deleting it, and keep the completed takes. Then resume only the missing subset. A one-line change like for L in ${LANES:-small ra} lets you rerun lane 2 alone. Have the resume wait on whichever comes first, the other side's 'window closed' post or the window's end time, and note in the results which takes ran before and after the window.