Add product search with autocomplete, filters, and sort

- Header: search button opening a command-palette dialog with debounced
  product suggestions, a term chip, and View All
- Command: shadcn-shaped primitives built on the project's own Dialog so
  no cmdk/radix dependency is introduced
- /search: results grid with item count, sort (relevance, price asc/desc),
  and cursor-based load more
- Filters: driven by the API's productFilters facets — colour swatches,
  labelled lists with counts, and a price range — round-tripped through
  each facet's raw input string so no filter shape is hardcoded

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016jWbNNJLksC1QG8z8845FX

graphql/search.js

@@ -0,0 +1,79 @@
+import { ProductFragment } from '@/graphql/products';
+
+// Storefront search over products. `productFilters` accepts the raw `input`
+// values returned in `productFilters[].values[].input`, so facets round-trip
+// without the client needing to know each filter's shape.
+export const SEARCH_PRODUCTS_QUERY = `
+  ${ProductFragment}
+  query SearchProducts(
+    $query: String!
+    $first: Int!
+    $after: String
+    $sortKey: SearchSortKeys
+    $reverse: Boolean
+    $productFilters: [ProductFilter!]
+  ) {
+    search(
+      query: $query
+      first: $first
+      after: $after
+      types: PRODUCT
+      sortKey: $sortKey
+      reverse: $reverse
+      productFilters: $productFilters
+    ) {
+      totalCount
+      pageInfo {
+        hasNextPage
+        endCursor
+      }
+      productFilters {
+        id
+        label
+        type
+        values {
+          id
+          label
+          count
+          input
+        }
+      }
+      edges {
+        node {
+          ... on Product {
+            ...ProductFragment
+          }
+        }
+      }
+    }
+  }
+`;
+
+// Lightweight variant for the autocomplete dropdown — just enough to render a
+// row, so the dialog stays responsive while typing.
+export const SEARCH_SUGGESTIONS_QUERY = `
+  query SearchSuggestions($query: String!, $first: Int!) {
+    search(query: $query, first: $first, types: PRODUCT) {
+      totalCount
+      edges {
+        node {
+          ... on Product {
+            id
+            title
+            handle
+            featuredImage {
+              url
+              altText
+            }
+            priceRange {
+              minVariantPrice {
+                amount
+                currencyCode
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+`;