test: migrate remaining 3 $app/forms consumers to shared mock

Completes Phase 1a after the load-bearing ChronikFuerDichBox spec proved
the pattern. ChronikFuerDichBox.test and NotificationDropdown.test (rich
result-firing interceptors) keep their submit-fired assertions
(optimisticMarkRead/MarkAllRead) and use formsMock.setFormResult for the
failure branch. NotificationBell.spec used the simpler intercept-only
factory and renders no form of its own, so it adopts the shared superset
purely as a render-time stub. Part of #560.

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

frontend/src/lib/activity/ChronikFuerDichBox.svelte.test.ts

@@ -3,36 +3,12 @@ import { cleanup, render } from 'vitest-browser-svelte';
 import { page } from 'vitest/browser';
 import ChronikFuerDichBox from './ChronikFuerDichBox.svelte';
 import type { NotificationItem } from '$lib/notification/notifications';
+import * as formsMock from '$mocks/$app/forms';
 
-const mockFormResult = vi.hoisted(() => ({ type: 'success' as string }));
-
-vi.mock('$app/forms', () => ({
-	enhance(
-		node: HTMLFormElement,
-		submit?: (opts: {
-			formData: FormData;
-		}) => (opts: {
-			result: { type: string; data?: Record<string, unknown> };
-			update: () => Promise<void>;
-		}) => Promise<void>
-	) {
-		const handler = async (e: Event) => {
-			e.preventDefault();
-			const cb = submit?.({ formData: new FormData(node) } as never);
-			if (typeof cb === 'function') {
-				await (
-					cb as (o: { result: typeof mockFormResult; update: () => Promise<void> }) => Promise<void>
-				)({ result: mockFormResult, update: async () => {} });
-			}
-		};
-		node.addEventListener('submit', handler);
-		return { destroy: () => node.removeEventListener('submit', handler) };
-	}
-}));
+vi.mock('$app/forms', () => ({ ...formsMock }));
 
 afterEach(() => {
 	cleanup();
-	mockFormResult.type = 'success';
 });
 
 const mention = (overrides: Partial<NotificationItem> = {}): NotificationItem => ({
@@ -160,7 +136,7 @@ describe('ChronikFuerDichBox', () => {
 	});
 
 	it('shows an accessible error banner when the dismiss action returns a failure', async () => {
-		mockFormResult.type = 'failure';
+		formsMock.setFormResult({ type: 'failure' });
 		render(ChronikFuerDichBox, {
 			props: {
 				unread: [mention({ id: 'err-1' })],

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

@@ -2,18 +2,10 @@ import { afterEach, describe, it, expect, vi } from 'vitest';
 import { cleanup, render } from 'vitest-browser-svelte';
 import type { NotificationItem } from '$lib/notification/notifications';
 import NotificationBell from './NotificationBell.svelte';
+import * as formsMock from '$mocks/$app/forms';
 
 vi.mock('$app/navigation', () => ({ goto: vi.fn(), beforeNavigate: vi.fn() }));
-vi.mock('$app/forms', () => ({
-	enhance(node: HTMLFormElement, submit?: (opts: { formData: FormData }) => unknown) {
-		const handler = (e: Event) => {
-			e.preventDefault();
-			submit?.({ formData: new FormData(node) } as never);
-		};
-		node.addEventListener('submit', handler);
-		return { destroy: () => node.removeEventListener('submit', handler) };
-	}
-}));
+vi.mock('$app/forms', () => ({ ...formsMock }));
 
 const mockNotificationList = vi.hoisted((): { value: NotificationItem[] } => ({ value: [] }));
 

frontend/src/lib/notification/NotificationDropdown.svelte.test.ts

@@ -3,41 +3,15 @@ import { cleanup, render } from 'vitest-browser-svelte';
 import { page } from 'vitest/browser';
 import { goto } from '$app/navigation';
 import NotificationDropdown from './NotificationDropdown.svelte';
+import * as formsMock from '$mocks/$app/forms';
 
 vi.mock('$app/navigation', () => ({ goto: vi.fn() }));
 
-// Configurable result for the enhance mock — tests that need failure set
-// mockFormResult.type = 'failure' before clicking.
-const mockFormResult = vi.hoisted(() => ({ type: 'success' as string }));
-
-// Invoke the SubmitFunction and always call the returned result callback with
-// mockFormResult so tests can exercise both success and failure branches.
-vi.mock('$app/forms', () => ({
-	enhance(
-		node: HTMLFormElement,
-		submit?: (opts: {
-			formData: FormData;
-		}) => (opts: {
-			result: { type: string; data?: Record<string, unknown> };
-			update: () => Promise<void>;
-		}) => Promise<void>
-	) {
-		const handler = async (e: Event) => {
-			e.preventDefault();
-			const cb = submit?.({ formData: new FormData(node) } as never);
-			if (typeof cb === 'function') {
-				await cb({ result: mockFormResult, update: async () => {} } as never);
-			}
-		};
-		node.addEventListener('submit', handler);
-		return { destroy: () => node.removeEventListener('submit', handler) };
-	}
-}));
+vi.mock('$app/forms', () => ({ ...formsMock }));
 
 afterEach(() => {
 	cleanup();
 	vi.clearAllMocks();
-	mockFormResult.type = 'success'; // reset to default after each test
 });
 
 const makeNotification = (overrides: Record<string, unknown> = {}) => ({
@@ -235,7 +209,7 @@ describe('NotificationDropdown', () => {
 	});
 
 	it('shows a role=alert error banner when mark-all-read returns a failure', async () => {
-		mockFormResult.type = 'failure';
+		formsMock.setFormResult({ type: 'failure' });
 		render(NotificationDropdown, {
 			props: {
 				notifications: [makeNotification()],
@@ -372,7 +346,7 @@ describe('NotificationDropdown', () => {
 	});
 
 	it('does NOT call onClose or goto when the dismiss action returns a failure', async () => {
-		mockFormResult.type = 'failure';
+		formsMock.setFormResult({ type: 'failure' });
 		const onClose = vi.fn();
 		const n = makeNotification({ id: 'n99', actorName: 'Bob' });
 		render(NotificationDropdown, {