When on_job callbacks call list_jobs() (which triggers _load_store),
the in-memory state is reloaded from disk, discarding the next_run_at_ms
updates that _on_timer is actively computing. This causes jobs to
re-trigger indefinitely on the next tick.
Add an _executing flag around the job execution loop. While set,
_load_store returns the cached store instead of reloading from disk.
Includes regression test.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Daniel PhangandClaude Opus 4.6