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

docs/web-ui.md

@@ -500,6 +500,11 @@ not ours.
   is sent as `null`). Targets stay immutable — cancel + new
   schedule is the retarget workaround. Refuses cancelled rows;
   returns the updated `WireSchedule` on success.
+- `POST /api/schedules/{id}/fire-now` — operator-initiated manual
+  fire (#467). Runs the per-target fan-out once immediately.
+  Recurring schedules keep their cadence (manual fire is additive);
+  one-shot schedules are consumed (cancelled afterwards). Manager
+  surface: `fire_schedule_now(id)` MCP tool.
 - `POST /api/schedules/{id}/cancel` — cancel a schedule. Body
   `{ targets?: ["name", …] }` cancels just those recipients;
   absent or empty body cancels the whole schedule.