Add Badge, Chip, and IconButton components with token layers

- Badge: 11 solid-colour variants (navy, info, success, error, warning + light variants, neutral, white) with icon slots
- Chip: bordered interactive element with selected, dismissible, and disabled states
- IconButton: circle/square shapes, 3 variants × 3 intents × 3 sizes, uses lucide-react icons
- Add badge and chip domain token layers to tokens.css
- Configure extendTailwindMerge in cn() to recognise custom font-size utilities (text-small, text-body, etc.)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/lib/utils.ts

@@ -1,5 +1,15 @@
 import { type ClassValue, clsx } from 'clsx'
-import { twMerge } from 'tailwind-merge'
+import { extendTailwindMerge } from 'tailwind-merge'
+
+const twMerge = extendTailwindMerge({
+  extend: {
+    classGroups: {
+      'font-size': [
+        { text: ['h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'intro', 'body', 'small', 'caption'] },
+      ],
+    },
+  },
+})
 
 export function cn(...inputs: ClassValue[]) {
   return twMerge(clsx(inputs))