Cmd+K doesn't focus on the Search input on Firefox Mac

Firefox on Mac maps Cmd+K to focus on the main browser address bar.

I believe sites like https://vercel.com/docs use `event.preventDefault()` to override this.

Other sites like https://grok.com/ don't (yet?) do this, which results in an awkward popup followed by focus moving to the address bar.  GitHub gets around it by using '/' instead, which I quite like.

Happy to push a PR if you like.
j.