Adds a periodic timer (default 30s) that calls drain() unconditionally,
covering the case where chokidar/inotify silently drops an IN_MODIFY
event. Observed twice in production: ping appended to inbox, file mtime
updated, but no event delivered to the watcher; a sibling-file touch
unblocked it. Root cause is Linux inotify under brief idle gaps + atomic
writes — not consistently reliable on its own.
drain() is already idempotent (HWM comparison short-circuits when
nothing's new), so the steady-state overhead is one stat + JSON parse
per poll cycle. Event-driven path remains the primary; the poll just
masks the rare miss within the cycle interval.
- safetyPollMs option: default 30_000, set to 0 to disable
- stop() clears the interval before closing chokidar
- Two new tests: safety-poll delivers when fs-event never fires;
safetyPollMs:0 truly disables the timer
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
