Scaffold design engineering playground

Next.js 16 + TypeScript + Tailwind v4 + Motion project showcasing
interface components built on semantic design tokens:

- Light/dark/system theming from one CSS variable set, with a
  pre-paint script so a saved theme never flashes
- Button, Switch and SegmentedControl with keyboard support, ARIA
  semantics and spring motion that respects reduced-motion
- Vitest + Testing Library tests, including a token-coverage test
- /tokens page documenting colour and motion tokens

Co-Authored-By: Claude Opus 5.5 <[email protected]>

next.config.ts

@@ -0,0 +1,17 @@
+import type { NextConfig } from "next";
+
+const nextConfig: NextConfig = {
+  /* config options here */
+  cacheComponents: true,
+  partialPrefetching: true,
+  turbopack: {
+    rules: {
+      "*.css": {
+        loaders: ["@tailwindcss/turbopack"],
+        as: "*.css",
+      },
+    },
+  },
+};
+
+export default nextConfig;