feat(core-ui): add jsdom Vitest config + RTL tests for components

Adopts jsdomVitestConfig from @repo/core-typescript. Adds
@testing-library/react, @testing-library/user-event, jsdom devDeps.
Writes smoke + interaction tests for every atom/molecule/organism/template
using renderWithProviders from @repo/core-testing/react.

Components covered:
- atoms: Button (5 tests), Input (4), Label (2)
- molecules: FormField (5)
- organisms / templates: empty barrels, no components

Adjustments:
- core-ui/tsconfig.json now extends react-library.json (jsx: react-jsx)
  with rootDir "." + paths {"@/*"} + types [vitest/globals, jest-dom]
- core-typescript/vitest.base.jsdom.ts uses ./vitest.base.node.ts (explicit
  .ts extension) so Node's ESM resolver finds the source file when loaded
  via the package export from a downstream package

Spec: §6.1, §6.5

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/core-ui/package.json

@@ -10,7 +10,8 @@
   "scripts": {
     "build": "tsc --noEmit",
     "lint": "eslint .",
-    "typecheck": "tsc --noEmit"
+    "typecheck": "tsc --noEmit",
+    "test": "vitest run --passWithNoTests"
   },
   "dependencies": {
     "clsx": "^2.1.1",
@@ -19,8 +20,14 @@
   },
   "devDependencies": {
     "@repo/core-eslint": "workspace:*",
+    "@repo/core-testing": "workspace:*",
     "@repo/core-typescript": "workspace:*",
     "@storybook/react": "^8.6.0",
-    "@types/react": "^19.0.0"
+    "@testing-library/jest-dom": "^6.5.0",
+    "@testing-library/react": "^16.0.0",
+    "@testing-library/user-event": "^14.5.0",
+    "@types/react": "^19.0.0",
+    "jsdom": "^25.0.0",
+    "vitest": "^3.0.0"
   }
 }