The merge_jobs cleanup encoded the server's pid in the CRDT and checked
`kill(pid, 0)` to decide whether a "running" entry was stale. Two problems:
1. The cleanup runs *inside* the server, so checking whether the
server's own pid is alive is tautological — kill(self_pid, 0)
always succeeds.
2. `rebuild_and_restart` does an `execve()` re-exec, which keeps the
same pid. After re-exec, merge_jobs from the previous server
instance still encode "the current pid" — so the cleanup never
fires, and stories like 799/800 sit forever with status="running"
while no actual merge runs.
Switch to a per-process server-start-time captured lazily in a
`OnceLock<f64>` (reset by execve, so the new instance sees a fresh
boot-time). A merge_job's recorded start-time < current boot-time means
it came from a previous instance: stale, delete it.
Legacy pid-encoded entries decode to None and are also treated as stale.
MergeJob.pid → MergeJob.server_start_time. Tests updated.
dave
2a77f73ba4