docs: add fire_schedule_now tool and /api/schedules/{id}/fire-now endpoint (follow-up to #472)

docs/turn-loop.md

@@ -347,6 +347,11 @@ meta's.
   to cancel just those recipients (auto-cancels when every target
   is removed). Authorization: manager can cancel schedules it owns
   or any owned by a sub-agent in its topology subtree.
+- `fire_schedule_now(id)` — fire a scheduled prompt out of band.
+  Runs the per-target fan-out once immediately. Recurring schedules
+  keep their cadence (the manual fire is additive); one-shot
+  schedules are consumed by the fire and cancelled afterwards. Same
+  authorization rules as `cancel_schedule`.
 - `list_schedules()` — snapshot every schedule (active +
   cancelled-but-not-reaped): id, owner, body, per-target
   `last_fired_at` + `last_result`, `next_fire_at_unix`,