The watchdog added in 9359e9c ran in a subshell that inherited the slot
lock's file descriptor. When a job finished early, `kill $watchdog`
ended the subshell but not its `sleep` child. That orphaned sleep kept
the slot for up to TIMEOUT seconds. Two slots were held this way on
2026-09-23, and four jobs queued behind them.
The subshell now closes the lock fd before sleeping, and the cleanup
kills the watchdog's children before the watchdog itself.
Tested on Yggdrasil: a fast job exited 0, and a TIMEOUT=15 hang exited
137 with the TIMEOUT line. Afterwards no sleep process held any
slot lock.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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