test(stammbaum): cover animateView rAF tween + server 401/500 paths (#692)

Add a deterministic stubbed-rAF test for animateView's animated path (was only
covering the reduced-motion branch) and assert the server load redirects on 401
and throws on a network 500 (QA review).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/lib/person/genealogy/animateView.test.ts

@@ -15,3 +15,28 @@ describe('animateView (reduced motion)', () => {
 		cancel();
 	});
 });
+
+describe('animateView (animated path)', () => {
+	const from = { x: 0, y: 0, z: 1 };
+	const to = { x: 100, y: 0, z: 2 };
+
+	it('tweens across frames and lands exactly on the target', () => {
+		const frames: { x: number }[] = [];
+		const callbacks: FrameRequestCallback[] = [];
+		vi.stubGlobal('performance', { now: () => 0 });
+		vi.stubGlobal('requestAnimationFrame', (cb: FrameRequestCallback) => callbacks.push(cb));
+		vi.stubGlobal('cancelAnimationFrame', () => {});
+
+		animateView(from, to, (v) => frames.push(v), { durationMs: 100 });
+
+		callbacks[0](50); // t = 0.5 → an interpolated frame
+		callbacks[callbacks.length - 1](100); // t = 1 → exact target
+
+		expect(frames.length).toBeGreaterThanOrEqual(2);
+		expect(frames[0].x).toBeGreaterThan(0);
+		expect(frames[0].x).toBeLessThan(100);
+		expect(frames.at(-1)).toEqual(to);
+
+		vi.unstubAllGlobals();
+	});
+});