test(viewer): cover PdfViewer outdated-annotation notice + fetch errors

Outdated notice when fileHash mismatches, no notice when matching,
fetch error gracefully ignored, non-OK response ignored.

4 new tests covering ~8 branches.

Refs #496.

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

frontend/src/lib/document/viewer/PdfViewer.svelte.test.ts

@@ -142,4 +142,106 @@ describe('PdfViewer — loaded state', () => {
 			})
 		).not.toThrow();
 	});
+
+	it('shows the outdated-annotation notice when annotations have non-matching fileHash', async () => {
+		const fetchSpy = vi.spyOn(globalThis, 'fetch').mockResolvedValue(
+			new Response(
+				JSON.stringify([
+					{
+						id: 'a1',
+						documentId: 'test',
+						pageNumber: 1,
+						x: 0.1,
+						y: 0.1,
+						width: 0.1,
+						height: 0.1,
+						color: '#000',
+						createdAt: '2026-01-01T00:00:00Z',
+						fileHash: 'old-hash'
+					}
+				]),
+				{ status: 200, headers: { 'Content-Type': 'application/json' } }
+			)
+		);
+		try {
+			render(PdfViewer, {
+				url: '/api/documents/test/file',
+				documentId: 'test',
+				documentFileHash: 'new-hash'
+			});
+
+			await new Promise((r) => setTimeout(r, 100));
+			const notice = document.querySelector('[data-testid="annotation-outdated-notice"]');
+			expect(notice).not.toBeNull();
+		} finally {
+			fetchSpy.mockRestore();
+		}
+	});
+
+	it('does not show outdated-annotation notice when all annotations match', async () => {
+		const fetchSpy = vi.spyOn(globalThis, 'fetch').mockResolvedValue(
+			new Response(
+				JSON.stringify([
+					{
+						id: 'a1',
+						documentId: 'test',
+						pageNumber: 1,
+						x: 0.1,
+						y: 0.1,
+						width: 0.1,
+						height: 0.1,
+						color: '#000',
+						createdAt: '2026-01-01T00:00:00Z',
+						fileHash: 'matching-hash'
+					}
+				]),
+				{ status: 200, headers: { 'Content-Type': 'application/json' } }
+			)
+		);
+		try {
+			render(PdfViewer, {
+				url: '/api/documents/test/file',
+				documentId: 'test',
+				documentFileHash: 'matching-hash'
+			});
+
+			await new Promise((r) => setTimeout(r, 100));
+			const notice = document.querySelector('[data-testid="annotation-outdated-notice"]');
+			expect(notice).toBeNull();
+		} finally {
+			fetchSpy.mockRestore();
+		}
+	});
+
+	it('handles fetch error when loading annotations gracefully', async () => {
+		const fetchSpy = vi.spyOn(globalThis, 'fetch').mockRejectedValue(new Error('network'));
+		try {
+			expect(() =>
+				render(PdfViewer, {
+					url: '/api/documents/test/file',
+					documentId: 'test'
+				})
+			).not.toThrow();
+			await new Promise((r) => setTimeout(r, 50));
+		} finally {
+			fetchSpy.mockRestore();
+		}
+	});
+
+	it('handles non-OK fetch response when loading annotations', async () => {
+		const fetchSpy = vi
+			.spyOn(globalThis, 'fetch')
+			.mockResolvedValue(new Response('error', { status: 500 }));
+		try {
+			expect(() =>
+				render(PdfViewer, {
+					url: '/api/documents/test/file',
+					documentId: 'test'
+				})
+			).not.toThrow();
+			await new Promise((r) => setTimeout(r, 50));
+		} finally {
+			fetchSpy.mockRestore();
+		}
+	});
 });