swarm: named scheduled prompts for one or more agents, fired in each agent

swarm-controller keeps every scheduled prompt (id, name, agents, body,
anchor, interval, paused) as one document under one key of a new
`schedule-definitions` KV bucket, so each change is a single
compare-and-set and a prompt exists for all of its agents or none. It
writes each agent's key of a new `agent-schedules` bucket as the prompts
naming that agent, without names or other agents, after every change and
on a one-minute reconcile pass. It is the only writer of both, behind
GET/POST /api/schedules and PATCH/DELETE /api/schedules/{id}.
`swarmctl schedule add|list|edit|pause|resume|rm` drives those routes over
the controller socket.

An agent's own queue credential is granted one more subject, the direct
get of its own key in `agent-schedules`. A KV watch is not granted: its
consumer create subject carries no key, so it would cover every agent's.

hive-agent's new schedule ticker reads that key every 10 seconds and fires
due slots as the same `schedule:<id>` todo hive-c0re's worker pushes. Fire
times are anchor + k*interval; the last fired slot per schedule id is kept
in the state db, so a body edit or list refresh never moves or refires a
slot, downtime fires the latest missed slot once, a restart refires
nothing, a one-shot fires once, and paused slots are skipped.

Refs #4914

swarm-controller/README.md

@@ -41,6 +41,11 @@ The swarm's control plane. The swarm UI and `swarmctl` are its clients.
   webhooks (`GET /api/config-prs`, `/api/agents/{name}/config-pr`).
 - **Swarm-wide forge objects and webhooks** →
   [`docs/swarm/README.md`](../docs/swarm/README.md#swarm-wide-forge-objects).
+- **Scheduled prompts** — named prompts for one or more agents, kept in
+  the `schedule-definitions` KV bucket and written into each agent's key of
+  `agent-schedules`, both of which this daemon alone writes
+  (`GET`/`POST /api/schedules`, `PATCH`/`DELETE /api/schedules/{id}`); each
+  agent fires them itself → [`docs/swarm/schedules.md`](../docs/swarm/schedules.md).
 - **Relays** — each agent's terminal and turn-state header as SSE, agent
   icons, the cross-repo issue report, and the UI's quick links.