Slice 3 of the worker state and queue consolidation refactor.
- Add IQueueWaker / QueueWaker (singleton holding the wake semaphore).
- Add IQueuePicker / QueuePicker; raw SQL UPDATE...RETURNING moves out of
TaskRepository.GetNextQueuedAgentTaskAsync (deleted) and now also filters
on blocked_by_task_id IS NULL and writes started_at on claim.
- TaskStateService takes IQueueWaker directly; the Func<QueueService>
indirection is gone. State transitions to Queued auto-wake the dispatcher.
- QueueService waits via the shared waker and dispatches via the picker.
- Drop explicit _queue.WakeQueue() calls in WorkerHub.QueuePlanningSubtasksAsync
and ExternalMcpService.AddTask. The hub WakeQueue endpoint stays for
diagnostics, delegating to _waker.Wake().
- Migrate tests; pre-existing flaky AppSettings/ExternalMcp tests untouched.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
