fix(stammbaum): add × dismiss button with aria-label to StammbaumSidePanel

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

frontend/src/lib/components/StammbaumSidePanel.svelte.spec.ts

@@ -0,0 +1,46 @@
+import { describe, it, expect, afterEach, vi, beforeEach } from 'vitest';
+import { cleanup, render } from 'vitest-browser-svelte';
+import { page } from 'vitest/browser';
+import StammbaumSidePanel from './StammbaumSidePanel.svelte';
+
+vi.mock('$app/navigation', () => ({ invalidateAll: vi.fn() }));
+vi.mock('$lib/components/PersonTypeahead.svelte', () => ({ default: () => null }));
+
+const makeNode = () => ({
+	id: 'person-1',
+	displayName: 'Alice Müller',
+	birthYear: 1900,
+	deathYear: null,
+	familyMember: true
+});
+
+function stubFetch(directRels: unknown[] = [], inferredRels: unknown[] = []) {
+	let callCount = 0;
+	vi.stubGlobal(
+		'fetch',
+		vi.fn().mockImplementation(() => {
+			callCount++;
+			const body = callCount % 2 === 1 ? directRels : inferredRels;
+			return Promise.resolve({ ok: true, json: () => Promise.resolve(body) });
+		})
+	);
+}
+
+beforeEach(() => stubFetch());
+afterEach(() => {
+	cleanup();
+	vi.unstubAllGlobals();
+});
+
+describe('StammbaumSidePanel', () => {
+	it('calls onClose when dismiss button is clicked', async () => {
+		const onClose = vi.fn();
+		render(StammbaumSidePanel, { node: makeNode(), onClose, canWrite: false });
+		await expect.element(page.getByRole('button', { name: 'Schließen' })).toBeInTheDocument();
+		const btn = [...document.querySelectorAll<HTMLButtonElement>('button')].find(
+			(b) => b.getAttribute('aria-label') === 'Schließen'
+		);
+		btn!.click();
+		expect(onClose).toHaveBeenCalledOnce();
+	});
+});