feat(shared): add cn utility for tailwind-aware class merging

src/shared/lib/utils/cn.test.ts

@@ -0,0 +1,30 @@
+import {
+    describe,
+    expect,
+    it,
+} from 'vitest';
+import { cn } from './cn';
+
+describe('cn utility', () => {
+    it('should merge classes with clsx', () => {
+        expect(cn('class1', 'class2')).toBe('class1 class2');
+        expect(cn('class1', { class2: true, class3: false })).toBe('class1 class2');
+    });
+
+    it('should resolve tailwind specificity conflicts', () => {
+        // text-neutral-400 vs text-brand (text-brand should win)
+        expect(cn('text-neutral-400', 'text-brand')).toBe('text-brand');
+
+        // p-4 vs p-2
+        expect(cn('p-4', 'p-2')).toBe('p-2');
+
+        // dark mode classes should be handled correctly too
+        expect(cn('text-neutral-400 dark:text-neutral-400', 'text-brand dark:text-brand')).toBe(
+            'text-brand dark:text-brand',
+        );
+    });
+
+    it('should handle undefined and null inputs', () => {
+        expect(cn('class1', undefined, null, 'class2')).toBe('class1 class2');
+    });
+});