aidenybai/react-scan ? reverse-engineered prompt

Build me a developer tool that helps people find and fix performance issues in their React applications. It should be incredibly easy to add to an existing project—ideally with just a single npx command that handles installation and configuration automatically.

Once it's running in a development environment, the tool should detect when components re-render unnecessarily. When it finds a problem, it should highlight the slow component directly on the page with a noticeable, colored border. I'd also like a small, floating toolbar that appears on the site, letting the user toggle the scanning on or off.

This tool needs to work seamlessly with modern React frameworks like Next.js, Vite, and Remix, where installation is as simple as adding a script tag. It should essentially just work out of the box to help developers visualize what’s making their app slow.