test: cover DocumentThumbnail, UnsavedWarningBanner, PersonsStatsBar

DocumentThumbnail: thumbnailUrl→img branch, no-thumbnail→placeholder
icon branch, sm vs lg size container class, lazy/async loading attrs.

UnsavedWarningBanner: warning text, discard button, callback wiring.

PersonsStatsBar: count rendering, singular/plural label switching for
both persons and documents (4 branches), zero-count plural fallback.

14 tests across three small primitive files.

Refs #496.

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

frontend/src/lib/document/DocumentThumbnail.svelte.test.ts

@@ -0,0 +1,61 @@
+import { describe, it, expect, afterEach } from 'vitest';
+import { cleanup, render } from 'vitest-browser-svelte';
+import DocumentThumbnail from './DocumentThumbnail.svelte';
+
+afterEach(cleanup);
+
+describe('DocumentThumbnail', () => {
+	it('renders the supplied thumbnail image when thumbnailUrl is set', async () => {
+		render(DocumentThumbnail, {
+			props: {
+				doc: { id: 'd1', thumbnailUrl: '/api/d1/thumb', contentType: 'application/pdf' }
+			}
+		});
+
+		const img = document.querySelector('img') as HTMLImageElement;
+		expect(img).not.toBeNull();
+		expect(img.src).toContain('/api/d1/thumb');
+	});
+
+	it('renders the placeholder icon when thumbnailUrl is missing', async () => {
+		render(DocumentThumbnail, {
+			props: { doc: { id: 'd1', thumbnailUrl: null, contentType: 'application/pdf' } }
+		});
+
+		const svg = document.querySelector('svg');
+		expect(svg).not.toBeNull();
+	});
+
+	it('uses the small container size by default', async () => {
+		render(DocumentThumbnail, {
+			props: { doc: { id: 'd1', thumbnailUrl: null, contentType: 'application/pdf' } }
+		});
+
+		const container = document.querySelector('.h-\\[84px\\]');
+		expect(container).not.toBeNull();
+	});
+
+	it('uses the large container size when size="lg"', async () => {
+		render(DocumentThumbnail, {
+			props: {
+				doc: { id: 'd1', thumbnailUrl: null, contentType: 'application/pdf' },
+				size: 'lg'
+			}
+		});
+
+		const container = document.querySelector('.h-\\[168px\\]');
+		expect(container).not.toBeNull();
+	});
+
+	it('uses lazy loading attributes on the thumbnail image', async () => {
+		render(DocumentThumbnail, {
+			props: {
+				doc: { id: 'd1', thumbnailUrl: '/api/d1/thumb', contentType: 'application/pdf' }
+			}
+		});
+
+		const img = document.querySelector('img') as HTMLImageElement;
+		expect(img.loading).toBe('lazy');
+		expect(img.decoding).toBe('async');
+	});
+});