Add collections pagination and a search field on the search page

Paginate the collections grid with a "See more" button backed by a new
getCollectionsPage cursor API, add an editable search input to the
search-results block, and bump @shopify/hydrogen to 2026.10.0-preview.1.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DqFkSaLYRPZ18dsMbzjiP4

components/shopify/search-results.editor.tsx

@@ -4,6 +4,7 @@ import SearchResults from '@/components/shopify/search-results';
 
 export type SearchResultsBlockProps = {
   title?: string;
+  placeholder?: string;
 };
 
 const searchResultsEditor: ComponentConfig<SearchResultsBlockProps> = {
@@ -12,9 +13,11 @@ const searchResultsEditor: ComponentConfig<SearchResultsBlockProps> = {
   category: 'commerce',
   defaultProps: {
     title: 'Search',
+    placeholder: 'Search products',
   },
   fields: {
     title: { label: 'Title', type: 'text', contentEditable: true },
+    placeholder: { label: 'Search placeholder', type: 'text' },
   },
   render: (props) => <SearchResults {...props} />,
 };