dashboard: queued reminders surface

new 'qu3u3d r3m1nd3rs' section between approvals and operator
inbox. lists every pending reminder with agent, due-relative
timestamp, body, payload path (path-linkified), and a cancel
button. drives off a new /api/reminders endpoint and a
POST /cancel-reminder/{id} that hard-deletes the row.

failure surface (last_error / attempt_count + retry) deferred —
needs a sqlite migration; tracked in TODO.md.

hive-c0re/assets/app.js

@@ -1240,6 +1240,79 @@
     return s.length <= n ? s : s.slice(0, n - 1) + '…';
   }
 
+  // ─── 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.
+  async function refreshReminders() {
+    const root = $('reminders-section');
+    if (!root) return;
+    try {
+      const resp = await fetch('/api/reminders');
+      if (!resp.ok) {
+        root.innerHTML = '';
+        root.append(el('p', { class: 'empty' }, 'reminders unavailable: http ' + resp.status));
+        return;
+      }
+      const rows = await resp.json();
+      renderReminders(rows);
+    } catch (err) {
+      root.innerHTML = '';
+      root.append(el('p', { class: 'empty' }, 'reminders fetch failed: ' + err));
+    }
+  }
+  function renderReminders(rows) {
+    const root = $('reminders-section');
+    if (!root) return;
+    root.innerHTML = '';
+    if (!rows.length) {
+      root.append(el('p', { class: 'empty' }, 'no queued reminders'));
+      return;
+    }
+    const ul = el('ul', { class: 'reminders' });
+    for (const r of rows) {
+      const li = el('li', { class: 'reminder-row' });
+      const dueIn = r.due_at - Math.floor(Date.now() / 1000);
+      const dueLabel = dueIn <= 0
+        ? `overdue ${fmtAgo(r.due_at)}`
+        : `in ${fmtDuration(dueIn)}`;
+      const head = el('div', { class: 'reminder-head' },
+        el('span', { class: 'agent' }, r.agent), ' ',
+        el('span', { class: 'meta', title: new Date(r.due_at * 1000).toISOString() }, dueLabel),
+        ' ',
+        el('span', { class: 'meta' }, `· id ${r.id}`),
+      );
+      if (r.file_path) {
+        head.append(' ', el('span', { class: 'meta' }, '· payload → '));
+        appendLinkified(head, r.file_path);
+      }
+      const body = el('div', { class: 'reminder-body' });
+      const previews = appendLinkified(body, r.message);
+      li.append(head, body);
+      for (const d of previews) li.appendChild(d);
+      // Cancel form omits `data-no-refresh` — the resulting refreshState
+      // re-fires refreshReminders so the row drops on its own.
+      const cancelForm = el('form', {
+        method: 'POST', action: '/cancel-reminder/' + r.id,
+        class: 'inline', 'data-async': '',
+        'data-confirm': `cancel reminder ${r.id} for ${r.agent}? this drops the queued delivery; no undo.`,
+      });
+      cancelForm.append(el('button', { type: 'submit', class: 'btn btn-deny' }, '✗ C4NC3L'));
+      li.append(cancelForm);
+      ul.append(li);
+    }
+    root.append(ul);
+  }
+  function fmtDuration(secs) {
+    if (secs < 60) return secs + 's';
+    if (secs < 3600) return Math.floor(secs / 60) + 'm ' + (secs % 60) + 's';
+    if (secs < 86400) return Math.floor(secs / 3600) + 'h ' + Math.floor((secs % 3600) / 60) + 'm';
+    return Math.floor(secs / 86400) + 'd ' + Math.floor((secs % 86400) / 3600) + 'h';
+  }
+
   // ─── state polling ──────────────────────────────────────────────────────
   let pollTimer = null;
   // Sections whose innerHTML gets blown away on each refresh. If the
@@ -1252,6 +1325,7 @@
     'inbox-section',
     'approvals-section',
     'meta-inputs-section',
+    'reminders-section',
   ];
   // <details> sections that should survive a refresh need a stable
   // `data-restore-key` attribute. snapshotOpenDetails walks managed
@@ -1326,6 +1400,7 @@
       syncApprovalsFromSnapshot(s);
       renderApprovals();
       renderMetaInputs(s);
+      refreshReminders();
       restoreOpenDetails(openDetails);
       notifyDeltas(s);
       // No periodic refresh timer. Phase 6 covers every container