Hide the synthetic Default Title option on single-SKU products

Shopify gives every single-variant product one option named Title with the
lone value Default Title. It isn't a real choice, so filter it out of the
product detail options, the cart line summaries, and the payload the store
assistant sees. Variant matching still reads the raw selectedOptions, so
single-SKU products keep resolving their variant.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EuRVxuyMUTzWKXW8P5Tn8A

components/shopify/cart-drawer.tsx

@@ -25,6 +25,7 @@ import {
   EmptyDescription,
   EmptyContent,
 } from '@/components/ui/empty';
+import { isDefaultTitleSelection } from '@/services/shopify/catalog';
 
 const CartDrawer: React.FC = () => {
   const isOpen = useCartStore((s) => s.isOpen);
@@ -102,7 +103,10 @@ const CartDrawer: React.FC = () => {
   };
 
   const getSelectedOptions = (item: (typeof items)[0]) => {
-    return item.merchandise.selectedOptions ?? [];
+    // Single-SKU items carry a synthetic `Title: Default Title` — not worth a line.
+    return (item.merchandise.selectedOptions ?? []).filter(
+      (option) => !isDefaultTitleSelection(option)
+    );
   };
 
   return (