feat(schedules): make schedules pausable

Adds pause/resume support for scheduled prompts.

Backend:
- New paused_at_unix column on scheduled_prompts table (added via
  ALTER TABLE migration so existing databases are upgraded on first
  start). The due-rows index is dropped and recreated to also exclude
  paused rows so the worker never fires them while paused.
- Worker's due() query gains AND paused_at_unix IS NULL filter.
- New pause(id) and resume(id) methods on ScheduledPrompts; both are
  idempotent and refuse cancelled rows.
- New POST /api/schedules/{id}/pause and /api/schedules/{id}/resume
  dashboard endpoints (operator-direct, no approval gate). Both emit
  a schedules snapshot on success so the tab updates live.
- WireSchedule gains paused_at_unix: Option<i64> so the frontend can
  render the state without an extra fetch.

Frontend:
- Paused rows render with a distinct row class + muted opacity.
- The next-fire cell shows a yellow pause glyph + tooltip with the
  paused-since timestamp and the would-have-fired time.
- Actions column: pause/resume toggle button (⏸/▶) beside fire/edit/cancel.
  Fire-now is disabled while paused (resume first).
- Sort order: active → paused → cancelled (paused slot keeps schedules
  visible without mixing them into the active top section).
- pauseSchedule() / resumeSchedule() async functions POST to the new
  endpoints and refresh the table on success.

frontend/packages/dashboard/src/dashboard.css

@@ -1100,6 +1100,10 @@ footer .banner-thin {
   opacity: 0.75;
 }
 .schedules-table-row-cancelled td { opacity: 0.55; }
+.schedules-table-row-paused td { opacity: 0.75; }
+.sched-paused-label { color: var(--yellow); font-size: 0.9em; }
+.btn-pause-schedule { color: var(--teal); }
+.btn-resume-schedule { color: var(--green); }
 .schedules-table-body-cell {
   max-width: 30em;
   overflow: hidden;

frontend/packages/dashboard/src/schedules.js

@@ -390,9 +390,10 @@ function renderSchedulesList() {
     table.append(renderSchedulesTableHead(agents));
     const tbody = el('tbody', {});
     const sorted = schedulesState.slice().sort((a, b) => {
-      const aDone = a.cancelled_at_unix ? 1 : 0;
-      const bDone = b.cancelled_at_unix ? 1 : 0;
-      if (aDone !== bDone) return aDone - bDone;
+      // Cancelled → bucket 2, paused → bucket 1, active → bucket 0.
+      const aOrd = a.cancelled_at_unix ? 2 : a.paused_at_unix ? 1 : 0;
+      const bOrd = b.cancelled_at_unix ? 2 : b.paused_at_unix ? 1 : 0;
+      if (aOrd !== bOrd) return aOrd - bOrd;
       return a.next_fire_at_unix - b.next_fire_at_unix;
     });
     for (const s of sorted) {
@@ -637,8 +638,11 @@ function renderSchedulesTableHead(agents) {
 }
 function renderScheduleRow(s, agents) {
   const cancelled = !!s.cancelled_at_unix;
+  const paused = !cancelled && !!s.paused_at_unix;
   const tr = el('tr', {
-    class: 'schedules-table-row' + (cancelled ? ' schedules-table-row-cancelled' : ''),
+    class: 'schedules-table-row'
+      + (cancelled ? ' schedules-table-row-cancelled' : '')
+      + (paused ? ' schedules-table-row-paused' : ''),
   });
 
   tr.append(el('td', { class: 'meta schedules-table-id' }, '#' + s.id));
@@ -649,11 +653,20 @@ function renderScheduleRow(s, agents) {
       srcKind === 'approval' ? 'approval' : 'operator')));
 
   // "next" cell — relative due-in for active schedules, "cancelled"
-  // for cancelled ones. Both carry the absolute ISO in the title.
+  // for cancelled ones, "paused" for paused ones. Both carry the
+  // absolute ISO in the title.
   const nextCell = el('td', { class: 'meta schedules-table-next-col' });
   if (cancelled) {
     nextCell.title = 'cancelled ' + new Date(s.cancelled_at_unix * 1000).toISOString();
     nextCell.textContent = 'cancelled';
+  } else if (paused) {
+    nextCell.title = 'paused since '
+      + new Date(s.paused_at_unix * 1000).toISOString()
+      + '\nwould fire at '
+      + new Date(s.next_fire_at_unix * 1000).toISOString();
+    nextCell.append(
+      el('span', { class: 'sched-paused-label' }, '⏸ paused'),
+    );
   } else {
     const dueIn = s.next_fire_at_unix - Math.floor(Date.now() / 1000);
     nextCell.title = new Date(s.next_fire_at_unix * 1000).toISOString();
@@ -723,10 +736,10 @@ function renderScheduleRow(s, agents) {
     tr.append(td);
   }
 
-  // Actions cell — fire / edit / cancel-all. Glyph-only to fit a
-  // compact column; the buttons keep their existing colour classes
-  // so the visual cue (mauve = fire, yellow = edit, red = cancel)
-  // carries over from the card layout.
+  // Actions cell — fire / pause-toggle / edit / cancel-all.
+  // Glyph-only to fit a compact column; colour classes carry the
+  // visual cue: mauve = fire, teal = pause/resume, yellow = edit,
+  // red = cancel.
   const actionsCell = el('td', { class: 'schedules-table-actions' });
   if (!cancelled) {
     const activeTargets = (s.targets || []).filter((t) => !t.cancelled_at_unix);
@@ -738,14 +751,28 @@ function renderScheduleRow(s, agents) {
     fireBtn.title = isOneShot
       ? 'fire once — one-shot, consumed after the manual fire'
       : 'fire once now — recurring; choose whether to reset the next-fire timer';
-    if (!activeTargets.length) {
+    if (!activeTargets.length || paused) {
       fireBtn.disabled = true;
-      fireBtn.title = 'every target is cancelled — nothing to fire';
+      fireBtn.title = paused
+        ? 'resume the schedule first to use fire-now'
+        : 'every target is cancelled — nothing to fire';
     }
     fireBtn.addEventListener('click', () =>
       fireScheduleNow(s.id, isOneShot, activeTargets.map((t) => t.target), fireBtn));
     actionsCell.append(fireBtn);
 
+    // Pause / resume toggle — only meaningful for recurring schedules.
+    // One-shots can still be paused (to delay a one-time fire), so we
+    // show the button for both cases.
+    const pauseBtn = el('button', {
+      type: 'button',
+      class: 'btn btn-pause-schedule btn-inline-small' + (paused ? ' btn-resume-schedule' : ''),
+    }, paused ? '▶' : '⏸');
+    pauseBtn.title = paused ? 'resume schedule' : 'pause schedule';
+    pauseBtn.addEventListener('click', () =>
+      paused ? resumeSchedule(s.id) : pauseSchedule(s.id));
+    actionsCell.append(pauseBtn);
+
     const editingThis = editingSchedules.has(s.id);
     const editBtn = el('button', {
       type: 'button',
@@ -1089,6 +1116,37 @@ async function postScheduleCancel(id, targets) {
   }
 }
 
+async function pauseSchedule(id) {
+  try {
+    const resp = await fetch('/api/schedules/' + encodeURIComponent(id) + '/pause', {
+      method: 'POST',
+    });
+    if (!resp.ok) {
+      const text = await resp.text().catch(() => '');
+      themedToast('pause failed: http ' + resp.status + (text ? '\n\n' + text : ''), { type: 'error' });
+      return;
+    }
+    await refreshSchedules();
+  } catch (err) {
+    themedToast('pause failed: ' + err, { type: 'error' });
+  }
+}
+async function resumeSchedule(id) {
+  try {
+    const resp = await fetch('/api/schedules/' + encodeURIComponent(id) + '/resume', {
+      method: 'POST',
+    });
+    if (!resp.ok) {
+      const text = await resp.text().catch(() => '');
+      themedToast('resume failed: http ' + resp.status + (text ? '\n\n' + text : ''), { type: 'error' });
+      return;
+    }
+    await refreshSchedules();
+  } catch (err) {
+    themedToast('resume failed: ' + err, { type: 'error' });
+  }
+}
+
 export function applySchedulesChanged(ev) {
   schedulesState = (ev.schedules || []).slice();
   renderSchedulesList();