grafana/k6 ? reverse-engineered prompt

Build me a modern load testing tool like k6.

I want to be able to write test scripts in JavaScript, run them from the command line, and simulate lots of virtual users hitting an app with realistic traffic. The scripts should let me set things like ramp up stages, sleep between requests, and pass or fail based on thresholds like response time and status codes. It should feel simple enough for a developer to use in CI, but still powerful enough for serious performance testing.

Please make it support common web testing first, and leave room for other protocols too, like WebSockets and gRPC if that fits naturally. I’d also like useful test results, summaries, and a way to export metrics so they can be viewed elsewhere. If you need to check current docs or best practices while building it, go ahead and look them up.