This example demonstrates a minimal integration of React 19 and D3 v7, rendering a static “Hello D3 & React” message inside a React component. It shows how D3’s `select` function is used within a React `useEffect` hook to update the DOM element referenced by `useRef`. The app is mounted via `react-dom/client`’s `createRoot`, with dependencies loaded from a CDN import map. No data or interaction is present; the focus is on the boilerplate setup for combining these two libraries.