test(notification): make setNotifications authoritative in bell a11y tests

CI showed the single/many a11y tests failing with count 0: init()'s async
fetchUnreadCount resolved to {count:0} AFTER setNotifications() ran,
clobbering the seeded count (the flake Sara predicted in review). Stub
fetch to never settle so the announced count is driven solely by
setNotifications — deterministic, no race. Also rewrites the 'error' test
to seed a count then fail the load and assert the count SURVIVES, so it is
a meaningful state distinct from 'empty' (was byte-identical, flagged by
Felix/Sara/Leonie). Part of #560.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/lib/notification/NotificationBell.svelte.spec.ts

@@ -30,11 +30,12 @@ class NoopEventSource {
 
 beforeEach(() => {
 	vi.stubGlobal('EventSource', NoopEventSource);
+	// init()'s fetchUnreadCount() never settles, so the bell's announced count is
+	// driven solely by setNotifications() — removes the init-fetch-vs-setNotifications
+	// race (the real fetch would resolve to {count:0} and clobber the seeded count).
 	vi.stubGlobal(
 		'fetch',
-		vi
-			.fn()
-			.mockResolvedValue(new Response(JSON.stringify({ count: 0, content: [] }), { status: 200 }))
+		vi.fn(() => new Promise(() => {}))
 	);
 });
 
@@ -89,7 +90,6 @@ describe('NotificationBell — rendering', () => {
 describe('NotificationBell — announced unread count across a11y states', () => {
 	it('empty: announces no unread count and hides the live badge', async () => {
 		const { setNotifications } = renderBell();
-		await tick();
 		setNotifications([]);
 		await tick();
 
@@ -101,7 +101,6 @@ describe('NotificationBell — announced unread count across a11y states', () =>
 
 	it('single: announces one unread notification', async () => {
 		const { setNotifications } = renderBell();
-		await tick();
 		setNotifications([makeNotification({ id: 'n1', read: false })]);
 		await tick();
 
@@ -114,7 +113,6 @@ describe('NotificationBell — announced unread count across a11y states', () =>
 
 	it('many: announces the exact unread count', async () => {
 		const { setNotifications } = renderBell();
-		await tick();
 		setNotifications([
 			makeNotification({ id: 'n1', read: false }),
 			makeNotification({ id: 'n2', read: false }),
@@ -128,16 +126,21 @@ describe('NotificationBell — announced unread count across a11y states', () =>
 		expect(unreadBadge().textContent?.trim()).toBe('3');
 	});
 
-	it('error: degrades to a zero announced count when the unread-count load fails', async () => {
+	it('error: a failed unread-count load does not wipe the announced count', async () => {
 		vi.stubGlobal('fetch', vi.fn().mockRejectedValue(new Error('network down')));
-		renderBell();
+		const { setNotifications } = renderBell();
+		setNotifications([
+			makeNotification({ id: 'n1', read: false }),
+			makeNotification({ id: 'n2', read: false })
+		]);
 		await tick();
 
-		// A failed load leaves the count at 0; the bell still announces a valid,
-		// non-urgent state rather than a broken count.
+		// init()'s fetchUnreadCount rejects; its catch must leave the already-set
+		// count intact rather than silently zeroing the live region. This is a
+		// distinct state from "empty" — the count survived a transient load failure.
 		const btn = bellButton();
-		expect(btn.getAttribute('title')).toBe(m.notification_bell_label());
+		expect(btn.getAttribute('title')).toBe(m.notification_bell_unread_label({ count: 2 }));
 		expect(btn.getAttribute('aria-label')).toBe(btn.getAttribute('title'));
-		expect(unreadBadge().classList.contains('hidden')).toBe(true);
+		expect(unreadBadge().textContent?.trim()).toBe('2');
 	});
 });