Scaffolding baseline

webui/src/App.test.tsx

@@ -0,0 +1,16 @@
+import { render, screen } from '@testing-library/react'
+import { describe, expect, it } from 'vitest'
+import App from './App'
+
+describe('App', () => {
+  it('renders the ClusterCanvas shell', () => {
+    render(<App />)
+
+    expect(
+      screen.getByRole('heading', { name: 'ClusterCanvas' }),
+    ).toBeInTheDocument()
+    expect(
+      screen.getByRole('button', { name: 'Check service health' }),
+    ).toBeInTheDocument()
+  })
+})