test(logout): fix Cache API mock global typing for tsc

The intersected global type made `caches` non-optional, so `delete` failed
type-checking (TS2790). Cast to a fresh optional-typed shape so the mock can be
both assigned and deleted without using `any`.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

superset-frontend/src/features/home/RightMenu.test.tsx

@@ -401,17 +401,35 @@ test('Logs out and clears local storage item redux', async () => {
   expect(localStorage.getItem('redux')).not.toBeNull();
   expect(sessionStorage.getItem('login_attempted')).not.toBeNull();
 
-  await userEvent.hover(await screen.findByText(/Settings/i));
+  // Mock the Cache API so we can assert the namespaced store is purged.
+  const cacheGlobal = global as unknown as { caches?: CacheStorage };
+  const priorCaches = cacheGlobal.caches;
+  const deleteMock = jest.fn().mockResolvedValue(true);
+  cacheGlobal.caches = { delete: deleteMock } as unknown as CacheStorage;
 
-  // Simulate user clicking the logout button
-  const logoutButton = await screen.findByText('Logout');
-  await userEvent.click(logoutButton);
+  try {
+    await userEvent.hover(await screen.findByText(/Settings/i));
 
-  // Wait for local and session storage to be cleared
-  await waitFor(() => {
-    expect(localStorage.getItem('redux')).toBeNull();
-    expect(sessionStorage.getItem('login_attempted')).toBeNull();
-  });
+    // Simulate user clicking the logout button
+    const logoutButton = await screen.findByText('Logout');
+    await userEvent.click(logoutButton);
+
+    // Wait for local and session storage to be cleared
+    await waitFor(() => {
+      expect(localStorage.getItem('redux')).toBeNull();
+      expect(sessionStorage.getItem('login_attempted')).toBeNull();
+    });
+    // The namespaced Cache API store is purged on logout.
+    expect(deleteMock).toHaveBeenCalledWith('@SUPERSET-UI/CONNECTION');
+  } finally {
+    // Restore the global so an early assertion failure cannot leak the mock
+    // into other tests.
+    if (priorCaches === undefined) {
+      delete cacheGlobal.caches;
+    } else {
+      cacheGlobal.caches = priorCaches;
+    }
+  }
 });
 
 test('shows logout button when not embedded', async () => {

superset-frontend/src/features/home/RightMenu.tsx

@@ -28,6 +28,7 @@ import {
   getExtensionsRegistry,
   isFeatureEnabled,
   FeatureFlag,
+  CACHE_KEY,
 } from '@superset-ui/core';
 import {
   styled,
@@ -353,6 +354,14 @@ const RightMenu = ({
     try {
       window.localStorage.removeItem('redux');
       window.sessionStorage.removeItem('login_attempted');
+      // Purge the namespaced Cache API store so cached GET responses are not
+      // retained on the device after the session ends. Best-effort: the
+      // returned promise is not awaited since logout navigates away.
+      if (typeof caches !== 'undefined') {
+        caches.delete(CACHE_KEY).catch(() => {
+          /* best-effort: ignore cache deletion failures */
+        });
+      }
     } catch (error) {
       console.warn('Failed to clear storage on logout:', error);
     }