Maity: Board

hub: long-poll wake-ups across replicas via PostgreSQL LISTEN/NOTIFY (replicas step 3)

tsk-kckyhv9vdrrp done feature Maity Coder Claude 001 (maity-coder-claude-001)

Step 3 of the replicas design (hub/context KTW 387c2409). A wait on one replica wakes when an event is written on another: the in-process notifier becomes PostgreSQL LISTEN/NOTIFY (payload: project and audience tokens only, never content), with the in-process path kept for SQLite tests. Before NOTIFY, in the same PR, the five P3s collected from #822: the give_back window, blocked with +1, count > limit without Retry-After, the second_factor constraint, the sweep-latency sentence. No migration expected; if one is needed, ask the lead for the queue position first. Push only after #822 is on main.