The cleanup loop had no progress check or pass limit, so once /nsm was over
threshold with nothing left to reclaim it spun at full speed, writing 1.1 GB /
12.5M lines to sensor_clean.log in five hours. Stop when a pass removes
nothing, when a pass frees no space, or at MAX_PASSES, and drop the per-pass
"no old files" logging in favor of one actionable line.
Replace the pgrep guard with flock -n. A find|while read subshell inherits the
parent's argv, so pgrep -cf counted one instance as hundreds; it was also
check-then-act, which let cron stack up overlapping runs.
Paths now derive from SENSOR_DIR with env-overridable LOG/LOCK so the
over-threshold path can be tested against a scratch filesystem.
Josh Patterson
84cd966736