test(briefwechsel): expand CorrespondenzPersonBar coverage

Adds receiver-focus triggers correspondents fetch, advanced-filter
chevron rotation in both states.

3 new tests covering ~6 branches.

Refs #496.

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

frontend/src/routes/briefwechsel/CorrespondenzPersonBar.svelte.test.ts

@@ -92,4 +92,53 @@ describe('CorrespondenzPersonBar', () => {
 
 		expect(onswapPersons).toHaveBeenCalledOnce();
 	});
+
+	it('opens the suggestions dropdown on receiver focus when a senderId is set', async () => {
+		const fetchSpy = vi.spyOn(globalThis, 'fetch').mockResolvedValue(
+			new Response(JSON.stringify([{ id: 'p3', firstName: 'Carl', lastName: 'Brandt' }]), {
+				status: 200,
+				headers: { 'Content-Type': 'application/json' }
+			})
+		);
+		try {
+			render(CorrespondenzPersonBar, {
+				props: baseProps({ senderId: 'p1', receiverId: '' })
+			});
+
+			// Find the second PersonTypeahead input (Korrespondent) and trigger focus event
+			const inputs = document.querySelectorAll('input[type="text"]');
+			const corrInput = inputs[inputs.length - 1] as HTMLInputElement;
+			corrInput.dispatchEvent(new Event('focus', { bubbles: true }));
+
+			await new Promise((r) => setTimeout(r, 100));
+			// No assertion on the suggestions dropdown UI (component-internal),
+			// just confirm the fetch was made
+			expect(fetchSpy).toHaveBeenCalled();
+		} finally {
+			fetchSpy.mockRestore();
+		}
+	});
+
+	it('does not show advanced filter chevron rotation when showAdvanced is false', async () => {
+		render(CorrespondenzPersonBar, { props: baseProps({ showAdvanced: false }) });
+
+		// The filter toggle button has a chevron — should NOT be rotated
+		const buttons = document.querySelectorAll('button');
+		const filterBtn = Array.from(buttons).find((b) =>
+			b.textContent?.toLowerCase().includes('filter')
+		);
+		const chevron = filterBtn?.querySelector('img');
+		expect(chevron?.getAttribute('class')).not.toContain('rotate-180');
+	});
+
+	it('rotates the filter chevron when showAdvanced is true', async () => {
+		render(CorrespondenzPersonBar, { props: baseProps({ showAdvanced: true }) });
+
+		const buttons = document.querySelectorAll('button');
+		const filterBtn = Array.from(buttons).find((b) =>
+			b.textContent?.toLowerCase().includes('filter')
+		);
+		const chevron = filterBtn?.querySelector('img');
+		expect(chevron?.getAttribute('class')).toContain('rotate-180');
+	});
 });