stock check, variants in cart, variant buttons in product page

app/Catalog/ProductCard.php

@@ -19,7 +19,7 @@ final class ProductCard
 {
     /**
      * @param  array<string, mixed>  $product  one item from ProductService's localized array shape
-     * @return array{name: ?string, price: ?string, image: ?string, href: string}
+     * @return array{name: ?string, price: ?string, image: ?string, href: string, variantId: ?int}
      */
     public static function fromIndexed(array $product): array
     {
@@ -28,6 +28,12 @@ public static function fromIndexed(array $product): array
             'price' => $product['price'],
             'image' => $product['media'][0]['url'] ?? null,
             'href' => route('product.show', ['id' => $product['id']]),
+            // The card's quick "Add to cart" always adds this variant, same
+            // default Modules\Core\Catalog\Services\ProductService::
+            // variantSummaries() and product/show.blade.php both use — no
+            // picker at listing-grid scope, unlike the product page's own
+            // color swatches.
+            'variantId' => $product['variants'][0]['id'] ?? null,
         ];
     }
 }