Add AI store assistant with catalogue tool calls

- /api/chat streams via AI SDK v7 through OpenRouter (OPENROUTER_API_KEY),
  with a store-specific system prompt and five read-only tools:
  searchCatalogue, getProductDetails, listCollections,
  getCollectionProducts, browseProducts
- Sidebar assistant on the right that opens from a launcher and expands,
  built on ai-elements (conversation, message, prompt-input, tool) with
  shimmer on in-flight tool calls
- Extract services/shopify/catalog.ts so the Storefront fetchers have no
  React imports and can run in a Route Handler; the client hooks now
  re-export from it
- ai-elements pulled in the canonical shadcn primitives, replacing the
  hand-rolled command/dialog/button variants; search dialog moved to the
  cmdk-based Command and CommandDialog forwards shouldFilter
- Pin shiki to ^3.19.0 to match streamdown and drop the duplicate copy
- Add .env.example documenting the required env vars

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

package.json

@@ -9,24 +9,38 @@
     },
     "version": "0.0.0",
     "dependencies": {
+        "@ai-sdk/react": "^4.0.47",
         "@next/swc-wasm-web": "16.2.10",
+        "@openrouter/ai-sdk-provider": "^3.0.0",
         "@remixicon/react": "^4.9.0",
         "@shopify/storefront-api-client": "^1.0.0",
+        "@streamdown/cjk": "^1.0.3",
+        "@streamdown/code": "^1.1.1",
+        "@streamdown/math": "^1.0.2",
+        "@streamdown/mermaid": "^1.0.2",
         "@supabase/supabase-js": "^2.51.0",
+        "ai": "^7",
         "class-variance-authority": "0.7.1",
         "clsx": "^2.1.1",
+        "cmdk": "^1.1.1",
         "embla-carousel-react": "^8.6.0",
         "framer-motion": "12.42.2",
         "input-otp": "^1.4.2",
         "lucide-react": "^0.562.0",
         "motion": "^12.23.26",
+        "nanoid": "^6.0.0",
         "next": "16.2.10",
+        "radix-ui": "^1.6.7",
         "react": "^19.0.0",
         "react-dom": "^19.0.0",
+        "shiki": "^3.19.0",
         "sonner": "^2.0.7",
+        "streamdown": "^2.5.0",
         "tailwind-merge": "^3.4.0",
         "tailwindcss": "^4",
         "tw-animate-css": "1.4.0",
+        "use-stick-to-bottom": "^1.1.6",
+        "zod": "^4.4.3",
         "zustand": "^5.0.11"
     },
     "devDependencies": {