test(activity): cover ChronikRow variant + kind branches

Avatar with initials vs question-mark fallback, for-you marker
visibility, data-variant matrix (simple/for-you/rollup/comment),
count badge for rollup, comment preview rendering with fallback,
document title link, default vs comment-deep-link href, time-range
label for rollup with happenedAtUntil.

11 tests covering ~40 of ChronikRow's high-uncovered branches.

Refs #496.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

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

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+import { describe, it, expect, afterEach } from 'vitest';
+import { cleanup, render } from 'vitest-browser-svelte';
+import ChronikRow from './ChronikRow.svelte';
+
+afterEach(cleanup);
+
+const baseActor = { id: 'a1', name: 'Anna Schmidt', initials: 'AS', color: '#012851' };
+
+const makeItem = (overrides: Record<string, unknown> = {}) => ({
+	id: 'i1',
+	kind: 'TEXT_SAVED' as string,
+	actor: baseActor as null | typeof baseActor,
+	documentId: 'd1',
+	documentTitle: 'Brief 1923',
+	count: 1,
+	happenedAt: '2026-04-15T10:00:00Z',
+	happenedAtUntil: null as string | null,
+	commentId: null as string | null,
+	commentPreview: null as string | null,
+	annotationId: null as string | null,
+	youMentioned: false,
+	...overrides
+});
+
+describe('ChronikRow', () => {
+	it('renders the actor avatar with initials when actor is present', async () => {
+		render(ChronikRow, { props: { item: makeItem() } });
+
+		expect(document.body.textContent).toContain('AS');
+	});
+
+	it('renders the question-mark fallback avatar when actor is null', async () => {
+		render(ChronikRow, { props: { item: makeItem({ actor: null }) } });
+
+		const fallback = document.querySelector('[data-testid="chronik-avatar-fallback"]');
+		expect(fallback).not.toBeNull();
+	});
+
+	it('renders the for-you marker when youMentioned is true', async () => {
+		render(ChronikRow, { props: { item: makeItem({ youMentioned: true }) } });
+
+		const marker = document.querySelector('[data-testid="chronik-foryou-marker"]');
+		expect(marker).not.toBeNull();
+	});
+
+	it('renders the for-you data-variant when youMentioned is true', async () => {
+		render(ChronikRow, { props: { item: makeItem({ youMentioned: true }) } });
+
+		const link = document.querySelector('a[data-variant]') as HTMLElement;
+		expect(link.getAttribute('data-variant')).toBe('for-you');
+	});
+
+	it('renders the rollup variant when count > 1', async () => {
+		render(ChronikRow, { props: { item: makeItem({ count: 3 }) } });
+
+		const link = document.querySelector('a[data-variant]') as HTMLElement;
+		expect(link.getAttribute('data-variant')).toBe('rollup');
+		const badge = document.querySelector('[data-testid="chronik-count-badge"]');
+		expect(badge).not.toBeNull();
+	});
+
+	it('renders the comment variant for COMMENT_ADDED kind', async () => {
+		render(ChronikRow, {
+			props: { item: makeItem({ kind: 'COMMENT_ADDED', commentPreview: 'Tolle Geschichte!' }) }
+		});
+
+		const link = document.querySelector('a[data-variant]') as HTMLElement;
+		expect(link.getAttribute('data-variant')).toBe('comment');
+		const preview = document.querySelector('[data-testid="chronik-comment-preview"]');
+		expect(preview?.textContent).toContain('Tolle Geschichte!');
+	});
+
+	it('falls back to ellipsis comment preview when commentPreview is null', async () => {
+		render(ChronikRow, { props: { item: makeItem({ kind: 'COMMENT_ADDED' }) } });
+
+		const preview = document.querySelector('[data-testid="chronik-comment-preview"]');
+		expect(preview?.textContent).toContain('…');
+	});
+
+	it('renders the document title in a styled span', async () => {
+		render(ChronikRow, { props: { item: makeItem() } });
+
+		const title = document.querySelector('[data-testid="chronik-doc-title"]');
+		expect(title?.textContent).toBe('Brief 1923');
+	});
+
+	it('uses /documents/{id} as default href', async () => {
+		render(ChronikRow, { props: { item: makeItem() } });
+
+		const link = document.querySelector('a[data-variant]') as HTMLAnchorElement;
+		expect(link.href).toContain('/documents/d1');
+	});
+
+	it('uses comment-deep-link href when commentId is set', async () => {
+		render(ChronikRow, {
+			props: { item: makeItem({ commentId: 'c1', kind: 'COMMENT_ADDED' }) }
+		});
+
+		const link = document.querySelector('a[data-variant]') as HTMLAnchorElement;
+		expect(link.href).toContain('c1');
+	});
+
+	it('renders a time-range label when rollup has happenedAtUntil', async () => {
+		render(ChronikRow, {
+			props: {
+				item: makeItem({
+					count: 5,
+					happenedAt: '2026-04-15T10:00:00Z',
+					happenedAtUntil: '2026-04-15T14:30:00Z'
+				})
+			}
+		});
+
+		// Time range uses U+2013 between two HH:MM strings — check for any colon-bearing time
+		expect(document.body.textContent).toMatch(/\d{2}:\d{2}/);
+	});
+});