Invalidating cache with Diazo theme

I noticed that a change in my theme's css required a hard refresh to appear. Indeed, whether I use the Barceloneta theme or my own, all other css resources are downloaded with a ?version= timestamp but the theme css are not. I am using the without-caching-proxy cache profile which makes it use strongCaching. That seems appropriate, and appending a version timestamp will invalidate it, but obviously we don't have that here.

So what is the intended mechanism for invalidating a cache of theme css? I have thought about trying to instead register my css as a resource bundle with a last compiled date, and maybe taking the production-css line out of manifest.cfg but that is not ideal because it would decouple the registered css from the them (assuming it even works).

Ok I kept doing a search through all docs and google searches for invalidating caching and found nothing. And I completely missed that there is a "clear cache" button on the theme control panel...