sync-event toasts, image pull ordering, stale banner field diff

- replace chat-bot sync notifications with a dedicated relay_sync_events
  queue: POST/GET /api/sync-events, drained by /api/relay/poll and
  surfaced as stacking toasts via caldav.js. Old /api/chat/bot removed,
  bot=1 rows purged on bootstrap, orange bot rendering dropped from
  relay UI. Chat thread stays clean.
- collab pull: fetch attachments BEFORE applying the body so the moment
  state.cards reflects the new reference the file is on disk. Fixes the
  "preview shows broken/missing image, editor shows it" race where the
  browser cached the 404 between attachment landing and user re-render.
- detail stale banner now compares title/body/color/tags in addition to
  updated_at — robust against second-granularity timestamp collisions
  and any other case where updated_at doesn't tick but content differs.

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

public/js/modules/caldav.js

@@ -190,6 +190,7 @@ export async function triggerSync() {
     const relayRes = await fetch('api/relay/poll', {
         method: 'POST', headers: { 'X-CSRF-Token': getCsrf() },
     }).then(r => r.ok ? r.json() : null).catch(() => null);
+    drainSyncEvents(relayRes);
 
     if (res.ok) {
         const s = res.stats || {};
@@ -265,6 +266,7 @@ $('relay-test')?.addEventListener('click', async () => {
     if (res?.ok) {
         setRelayStatus(`ok — ${res.pulled} pulled`, 'success');
         if (res.pulled) await window._reloadAll?.();
+        drainSyncEvents(res);
     } else {
         const detail = res?.sent_username ? ` (sent username: ${res.sent_username})` : '';
         setRelayStatus((res?.error || 'failed') + detail, 'error');
@@ -315,6 +317,33 @@ function showSyncNotification(stats) {
     setTimeout(() => { note.style.transition = 'opacity 0.3s'; note.style.opacity = '0'; setTimeout(() => note.remove(), 350); }, 4000);
 }
 
+// One toast per incoming sync event: "alice synced: Card Title".
+// Stacks downward so a burst of multiple doesn't overlay each other.
+let syncEventToastOffset = 0;
+function showSyncEventToast(ev) {
+    const body = String(ev?.body || '').trim();
+    if (!body) return;
+    const bottom = 110 + syncEventToastOffset * 48;
+    syncEventToastOffset++;
+    const note = document.createElement('div');
+    note.style.cssText = `position:fixed;bottom:${bottom}px;right:16px;z-index:200;background:var(--t-surface);border:1px solid var(--t-accent2);border-radius:4px;padding:9px 14px;box-shadow:0 4px 20px rgba(0,0,0,0.4);max-width:320px;`;
+    note.innerHTML = `<div style="font-family:var(--t-font-pixel);font-size:10px;color:var(--t-accent2);display:flex;align-items:center;gap:6px;"><i class="ph ph-check-circle"></i>${body.replace(/[&<>"']/g, c => ({'&':'&amp;','<':'&lt;','>':'&gt;','"':'&quot;',"'":'&#39;'}[c]))}</div>`;
+    document.body.appendChild(note);
+    setTimeout(() => {
+        note.style.transition = 'opacity 0.3s';
+        note.style.opacity = '0';
+        setTimeout(() => {
+            note.remove();
+            syncEventToastOffset = Math.max(0, syncEventToastOffset - 1);
+        }, 350);
+    }, 5000);
+}
+
+function drainSyncEvents(relayRes) {
+    const events = Array.isArray(relayRes?.sync_events) ? relayRes.sync_events : [];
+    for (const ev of events) showSyncEventToast(ev);
+}
+
 async function backgroundSync() {
     if (state.bgSyncRunning) return;
     state.bgSyncRunning = true;
@@ -331,6 +360,7 @@ async function backgroundSync() {
             await window._reloadAll?.();
             showSyncNotification(total);
         }
+        drainSyncEvents(relayRes);
     } catch {} finally {
         state.bgSyncRunning = false;
     }