fix(fullstack): widen tier-2 reseed bound and add failure diagnostics (#1079)

Three seeded attempts over ~21s still delivered nothing in CI, so the
rejoined-channel issue is not a sub-second activation race. Widen to 6
attempts (~45s) to separate 'slow binding activation' from 'never
delivers', and on final failure include the island's live status and
rendered event count so the next red run tells us which world we are in.

Co-authored-by: DevBot <devbot@openelement.dev>

Author: SisyphusZheng

tools/smoke-supabase-browser.ts

@@ -45,7 +45,7 @@ async function seedNoteUntilDelivered(
   marker: string,
   title: string,
 ): Promise<void> {
-  for (let attempt = 1; attempt <= 3; attempt++) {
+  for (let attempt = 1; attempt <= 6; attempt++) {
     const insert = await fetch(`${supabaseUrl}/rest/v1/notes`, {
       method: 'POST',
       headers: {
@@ -64,7 +64,14 @@ async function seedNoteUntilDelivered(
       .then(() => true, () => false);
     if (delivered) return;
   }
-  throw new Error(`Realtime seed "${marker}" was not delivered after 3 bounded attempts`);
+  // Diagnostics for CI-only failures: is the island stuck pre-subscribe, or
+  // subscribed-but-silent?
+  const status = await live.locator('#live-status').innerText().catch(() => 'unreadable');
+  const events = await live.locator('#live-events li').count().catch(() => -1);
+  throw new Error(
+    `Realtime seed "${marker}" was not delivered after 6 bounded attempts ` +
+      `(island status: "${status}", live events rendered: ${events})`,
+  );
 }
 
 const browser = await chromium.launch();