Add `SchedulesChanged` to the dashboard event channel so the
operator's schedule list updates in real time without requiring a
tab-activation or form-submit refresh.
Backend:
- `dashboard_events.rs`: new `SchedulesChanged { seq, schedules }`
variant carrying a full `Vec<WireSchedule>` snapshot (same
snapshot-over-diff rationale as `RebuildQueueChanged`).
- `coordinator.rs`: `emit_schedules_snapshot()` helper — queries the
scheduled_prompts list, converts to wire shape, broadcasts the event.
- `dashboard.rs`: call `emit_schedules_snapshot()` at the end of each
operator API handler that mutates a schedule:
`post_schedule_new`, `post_schedule_fire_now`,
`patch_schedule`, `post_schedule_cancel`.
- `scheduled_prompts_worker.rs`: call `emit_schedules_snapshot()`
after each tick that fires schedules, so `last_fired_at_unix`,
`next_fire_at_unix`, and reaped one-shots surface live.
Frontend:
- `tabs.js`: add `applySchedulesChanged(ev)` — replaces
`schedulesState` from the snapshot and calls `renderSchedulesList()`.
Registered in `MUTATION_HANDLERS` as `schedules_changed`.
Tab-activation re-fetch kept as safety net for approval-path
inserts and disconnect windows; comment updated to reflect this.
Docs:
- `docs/web-ui/dashboard.md`: document `schedules_changed` event.
- `CLAUDE.md`: add `SchedulesChanged` to the file-map entry.
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