test(core): remove flaky toast assertion in shipping addProductAndGoToCart helper

Apply the same fix as cart and coupon tests: the add-to-cart success
toast auto-dismisses after ~4s, so asserting on it is racy and made
the shipping tests time out before reaching the cart page assertions.
Wait for networkidle instead.

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

Author: chanceaclark

core/tests/ui/e2e/shipping.spec.ts

@@ -10,14 +10,9 @@ async function addProductAndGoToCart(page: Page, catalog: CatalogFixture) {
 
   await page.goto(product.path);
   await page.getByRole('button', { name: t('Product.ProductDetails.Submit.addToCart') }).click();
-
-  // eslint-disable-next-line @typescript-eslint/consistent-type-assertions
-  const addToCartSuccessMessage = t.rich('Product.ProductDetails.successMessage', {
-    cartItems: 1,
-    cartLink: (chunks: React.ReactNode) => chunks,
-  }) as string;
-
-  await expect(page.getByText(addToCartSuccessMessage)).toBeVisible();
+  // The success toast auto-dismisses after ~4s, so asserting on it is racy.
+  // Wait for the add-to-cart action to settle and verify state via the /cart page instead.
+  await page.waitForLoadState('networkidle');
 
   await page.goto('/cart');
   await expect(page.getByRole('heading', { name: t('Cart.title') })).toBeVisible();