fixes: scratchpad, zen ESC, chat time, tooltip safety, collab sync race

- Scratchpad: card-scoped private notes in editor (toggle vs preview),
  smaller font, cleared via button, stored in cards.scratchpad
- Zen mode: ESC exits zen before closing detail, Z toggles zen
- Chat: always show absolute time (hh:mm, yesterday, or date+time)
- Backspace/Delete also deletes focused card (not just selected)
- Selected + focused cards use brand accent (not accent2)
- Tooltip: guard against non-element targets
- Collab sync: skip poll while editor is open, 2s push debounce
- Rrule test: only check geburtstag tag, not title format

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

relay/ui/app.js

@@ -722,7 +722,7 @@ async function loadChatHistory(peer, quiet = false) {
     container.innerHTML = messages.map(m => `
         <div class="chat-msg ${m.mine ? 'mine' : 'theirs'}">
             <div>${escapeHtml(m.body)}</div>
-            <div class="msg-time">${formatRelTime(m.created_at)}${m.mine && m.seen ? ' <i class="ph ph-checks"></i>' : ''}</div>
+            <div class="msg-time">${formatChatTime(m.created_at)}${m.mine && m.seen ? ' <i class="ph ph-checks"></i>' : ''}</div>
         </div>
     `).join('');
 
@@ -750,6 +750,18 @@ $('chat-input')?.addEventListener('keydown', e => {
     if (e.key === 'Enter' && !e.shiftKey) { e.preventDefault(); sendChatMessage(); }
 });
 
+function formatChatTime(sqliteUtc) {
+    if (!sqliteUtc) return '';
+    const t = new Date(sqliteUtc.replace(' ', 'T') + 'Z');
+    if (isNaN(t.getTime())) return sqliteUtc;
+    const now = new Date();
+    const time = t.toLocaleTimeString(undefined, { hour: '2-digit', minute: '2-digit' });
+    if (t.toDateString() === now.toDateString()) return time;
+    const yesterday = new Date(now); yesterday.setDate(yesterday.getDate() - 1);
+    if (t.toDateString() === yesterday.toDateString()) return 'yesterday ' + time;
+    return t.toLocaleDateString(undefined, { month: 'short', day: 'numeric' }) + ' ' + time;
+}
+
 function formatRelTime(sqliteUtc) {
     if (!sqliteUtc) return '';
     // Parse SQLite's "YYYY-MM-DD HH:MM:SS" as UTC by appending Z