docs: document scheduled prompts tab in SYST3M (follow-up to #461)

docs/web-ui.md

@@ -218,6 +218,23 @@ button hard-deletes (`POST /cancel-reminder/{id}`) and a
 `R3TRY` button re-arms one whose delivery failed
 (`POST /retry-reminder/{id}`). Backed by `GET /api/reminders`.
 
+**SCH3DUL3D PR0MPTS** — operator-managed scheduled prompts
+(#444 / #459). Lists every schedule with its description,
+targets, body, recurrence interval, next-fire time, and
+per-target last-result; a `CANC3L` button cancels the whole
+schedule (`POST /api/schedules/{id}/cancel`), and individual
+target chips have their own cancel links. An inline creation
+form lets the operator queue a new schedule directly:
+targets (multi-select checkboxes drawn from live container
+names + `operator` + `manager`), prompt body (textarea),
+first-fire datetime-local (pre-filled to 5 minutes from now),
+optional recurrence interval in seconds (blank = one-shot),
+and an optional human-readable description. On submit the
+form POSTs to `/api/schedules` as JSON; the tab pill shows
+the count of active schedules (at least one live target not
+yet cancelled). Refreshed on tab activation and after each
+submit/cancel. Backed by `GET /api/schedules`.
+
 **K3PT ST4T3** — destroyed-but-state-kept tombstones (size +
 age + claude-creds badge). Two actions: `⊕ R3V1V3` (queues a
 Spawn approval; existing state is reused), `PURG3` (wipes
@@ -450,6 +467,15 @@ not ours.
 - `POST /cancel-reminder/{id}` — hard-delete a pending reminder.
 - `POST /retry-reminder/{id}` — re-arm a reminder whose delivery
   failed (clears the failure state so the scheduler retries).
+- `GET /api/schedules` — list all schedules (active and
+  recently cancelled) for the SYST3M scheduled-prompts panel.
+- `POST /api/schedules` — operator-direct schedule create:
+  `{ targets, body, first_fire_at_unix, interval_seconds?, description? }`.
+  Agent-initiated schedules go through the approval queue instead
+  (manager MCP `request_schedule_prompt`).
+- `POST /api/schedules/{id}/cancel` — cancel a schedule. Body
+  `{ targets?: ["name", …] }` cancels just those recipients;
+  absent or empty body cancels the whole schedule.
 - `POST /meta-update` — `nix flake update` the selected
   `meta/flake.lock` inputs, then rebuild the affected agents.
 - `GET /dashboard/stream` — unified live event channel: