*CTRL+BREAK* doesn't seem to work with all keyboards. This adds a new build command, *Kill*, which works reliably on Windows using *CTRL+ALT+B* (this is untested on other OSs). It will kill the most-recently launched chuck instance, and then the next most-recent, etc. Due to an ST bug, or perhaps ignorance on my part, it does not show up in the *Tools* menu (it should).
The unintended consequence here is that (afaict) *CTRL+SHIFT+B* won't kill multiple instances of chuck - only the most recent (or maybe the first; I haven't looked at it in detail).