Improving quality of search filters in Discourse AI

I think part of the problem here is that our search is a bit confusing:

https://meta.discourse.org/search?q=%23bug%20%23feature%20test

Searches for Contribute > Bug AND Contribute > Feature - test

What you want here is:

https://meta.discourse.org/search?q=categories%3Abug%2Cfeature%20test