test(core/hooks): add test for useAsyncEffect cleanup on early unmount

Covers the case where the component unmounts before the async effect's
Promise resolves — the previously missing scenario that allowed the
race condition bug to go undetected.

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

Author: eunwoo-levi

packages/core/src/hooks/useAsyncEffect/useAsyncEffect.spec.ts

@@ -89,6 +89,25 @@ describe('useAsyncEffect', () => {
     expect(cleanup).toHaveBeenCalled();
   });
 
+  it('should call cleanup even when component unmounts before async effect resolves', async () => {
+    const cleanup = vi.fn();
+    const { unmount } = await renderHookSSR(() =>
+      useAsyncEffect(async () => {
+        await new Promise(resolve => setTimeout(resolve, 1000));
+        return cleanup;
+      }, [])
+    );
+
+    await flushPromises();
+    unmount();
+    expect(cleanup).not.toHaveBeenCalled();
+
+    vi.advanceTimersByTime(1000);
+    await flushPromises();
+
+    expect(cleanup).toHaveBeenCalledTimes(1);
+  });
+
   it('should call effect every rerender when deps are undefined', async () => {
     const effect = vi.fn().mockResolvedValue(undefined);