The original write-tmp-then-rename guard handles the ETXTBSY race
on a vanilla filesystem, but inside the new ci-runner-go
container our jobs land on overlayfs, which keeps a lagged
"writable inode" view long enough to leak ETXTBSY into the
exec the test does milliseconds later.
After rename, probe-exec the file with a benign argument
("__rm_probe__" — every script's case statement falls through
to a clean exit) until exec succeeds. Each script body is shaped
`case "$1" in restore) ... ;; esac` so the probe is a no-op.
3s deadline keeps a stuck filesystem from hanging the suite.
steve