test(persons): expand persons/[id] page coverage

Co-correspondents derived from received-document senders, self-skip
branch when sender == current person, GeschichtenCard rendered when
geschichten array is non-empty, 5-entry cap on co-correspondents.

4 new tests covering ~10 branches.

Refs #496.

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

frontend/src/routes/persons/[id]/page.svelte.test.ts

@@ -101,4 +101,77 @@ describe('persons/[id] page', () => {
 			.element(page.getByRole('link', { name: /bearbeiten/i }))
 			.toHaveAttribute('href', '/persons/p-1/edit');
 	});
+
+	it('renders co-correspondents derived from received documents senders', async () => {
+		const data = baseData({
+			receivedDocuments: [
+				{
+					id: 'd-r1',
+					title: 'R1',
+					status: 'UPLOADED',
+					sender: { id: 's1', displayName: 'Carl Brandt' }
+				},
+				{
+					id: 'd-r2',
+					title: 'R2',
+					status: 'UPLOADED',
+					sender: { id: 's1', displayName: 'Carl Brandt' }
+				}
+			]
+		});
+		render(PersonDetailPage, { props: { data } });
+
+		expect(document.body.textContent).toContain('Carl Brandt');
+	});
+
+	it('skips the sender when sender id equals the current person id (loops cleanly)', async () => {
+		const data = baseData({
+			receivedDocuments: [
+				{
+					id: 'd-self',
+					title: 'Self-letter',
+					status: 'UPLOADED',
+					sender: { id: 'p-1', displayName: 'Anna Schmidt' }
+				}
+			]
+		});
+		// Just verify the page renders without error — the self-skip branch is exercised
+		expect(() => render(PersonDetailPage, { props: { data } })).not.toThrow();
+	});
+
+	it('renders the GeschichtenCard when geschichten array has items', async () => {
+		render(PersonDetailPage, {
+			props: {
+				data: baseData({
+					geschichten: [
+						{
+							id: 'g1',
+							title: 'Reise',
+							body: '<p>...</p>',
+							publishedAt: '2026-04-15T10:00:00Z'
+						}
+					]
+				})
+			}
+		});
+
+		expect(document.body.textContent).toContain('Reise');
+	});
+
+	it('caps the co-correspondents list at 5 entries', async () => {
+		const sent = Array.from({ length: 8 }, (_, i) => ({
+			id: `d-${i}`,
+			title: `Brief ${i}`,
+			status: 'UPLOADED',
+			receivers: [{ id: `r-${i}`, displayName: `Person ${i}` }]
+		}));
+		render(PersonDetailPage, { props: { data: baseData({ sentDocuments: sent }) } });
+
+		const correspondentsCard = Array.from(document.querySelectorAll('h2')).find((h) =>
+			/korrespondenten/i.test(h.textContent ?? '')
+		)?.parentElement;
+		const links = correspondentsCard?.querySelectorAll('a[href^="/persons/"]') ?? [];
+		// At most 5 person links inside the card
+		expect(links.length).toBeLessThanOrEqual(5);
+	});
 });