fix(dashboard): refresh reminders on SCH3DUL3S tab activation + update stale comments

- activateTab('schedules') now calls both refreshSchedules() and
  refreshReminders() since both sections live on the same tab.
  (The previous SYST3M/system target was wrong.)
- Update index.html comment to reflect schedules_changed SSE coverage
- Update index.html reminders comment to mention reminders_changed SSE
- Update tabs.js reminders section comment to reflect SSE coverage

frontend/packages/dashboard/src/tabs.js

@@ -2375,11 +2375,10 @@ window.marked = marked;
 
   // ─── reminders ──────────────────────────────────────────────────────────
   // Reminders aren't part of /api/state (separate sqlite table, separate
-  // mutation cadence). Refresh fires alongside refreshState() so a
-  // cancel POST or a cold load both reflect within the same tick. A
-  // periodic poll isn't necessary — new reminders are queued by the
-  // agents themselves and the operator already sees them next time
-  // they interact with the page.
+  // mutation cadence). refreshReminders() is called from refreshState() for
+  // cold-load and reconnect recovery. Live mutations are covered by the
+  // `reminders_changed` SSE event → `applyRemindersChanged` so no periodic
+  // poll is needed.
   async function refreshReminders() {
     const liveRoot = $('reminders-section');
     if (!liveRoot) return;
@@ -3664,8 +3663,10 @@ window.marked = marked;
     updateTabbarOverflow();
     // Re-fetch schedules on activation as a safety net (SSE covers
     // live mutations but re-sync ensures consistency after disconnect
-    // windows or approval-path inserts that don't yet emit).
-    if (target === 'schedules') refreshSchedules();
+    // windows or approval-path inserts that don't yet emit). Also
+    // re-fetch reminders on SCH3DUL3S activation since both sections
+    // live on the same tab.
+    if (target === 'schedules') { refreshSchedules(); refreshReminders(); }
     // Permissions tables (capabilities + tool-groups) have no SSE channel;
     // fetch both on each activation so the operator sees fresh data.
     if (target === 'permissions') {