feat: add core UI components and baseline tests

package.json

@@ -11,6 +11,8 @@
     "build:docs": "pnpm --filter @ai-ui/docs build-storybook",
     "dev:docs": "pnpm --filter @ai-ui/docs storybook",
     "lint": "eslint .",
+    "test": "pnpm --filter @ai-ui/ui test",
+    "test:watch": "pnpm --filter @ai-ui/ui test:watch",
     "typecheck": "pnpm -r typecheck"
   },
   "devDependencies": {
@@ -21,6 +23,9 @@
     "@storybook/react": "^8.6.14",
     "@storybook/react-vite": "^8.6.14",
     "@tailwindcss/vite": "^4.2.2",
+    "@testing-library/jest-dom": "^6.9.1",
+    "@testing-library/react": "^16.3.2",
+    "@testing-library/user-event": "^14.6.1",
     "@types/node": "^25.5.0",
     "@types/react": "^18.3.28",
     "@types/react-dom": "^18.3.7",
@@ -28,11 +33,13 @@
     "eslint-plugin-react-hooks": "^7.0.1",
     "eslint-plugin-react-refresh": "^0.5.2",
     "globals": "^17.4.0",
+    "jsdom": "^29.0.0",
     "storybook": "^8.6.14",
     "tailwindcss": "^4.2.2",
     "tsup": "^8.5.1",
     "typescript": "^5.9.3",
     "typescript-eslint": "^8.57.1",
-    "vite": "^6.4.1"
+    "vite": "^6.4.1",
+    "vitest": "^4.1.0"
   }
 }