Done. Also made it so png recordings don't show up in "Recent files" (exposed as a bool arg to sprite:saveCopyAs). Works fine.
I'll clean it up and try to get this merged tomorrow if I get time.
Would anyone be interested in a custom Aseprite build that fixes the Automatic Snapshot save dialog popping up all the time?
Edit: PR opened https://github.com/aseprite/aseprite/pull/3216 If you have a GitHub account please upvote this so the maintainers prioritize reviewing it!