chore: vitest 4 for web, cli, and e2e (#26668)

web/src/lib/__mocks__/intersection-observer.mock.ts

@@ -1,9 +1,11 @@
 import { vi } from 'vitest';
 
 export const getIntersectionObserverMock = () =>
-  vi.fn(() => ({
-    disconnect: vi.fn(),
-    observe: vi.fn(),
-    takeRecords: vi.fn(),
-    unobserve: vi.fn(),
-  }));
+  vi.fn(function () {
+    return {
+      disconnect: vi.fn(),
+      observe: vi.fn(),
+      takeRecords: vi.fn(),
+      unobserve: vi.fn(),
+    };
+  });