Task 13 of the slice plan. Drives the pending → done/failed
transitions:
- enqueue() pushes a Job and kicks the loop; loadFromDb()
rehydrates pending_jobs at startup so app restart resumes
in-flight work.
- drain() exposes a Promise for tests + graceful shutdown.
- Concurrency 1: a single async loop awaits each provider call
before the next, matching spec §2.2.
- 3-attempt backoff (default [0, 30s, 120s]; tests inject [0,0,0]).
Each failure logs ai.retry, increments pending_jobs.attempts,
and on the final attempt calls markAiFailed and emits onUpdate.
- emit() pushes the freshly-hydrated note to onUpdate (used by
Task 30 to fan out IPC note:updated events).
Verification: `npx vitest run tests/unit/AiWorker.test.ts`
4 passed. Suite total 41 / 41.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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