Refine the REPL #478
Description
It's time to thoroughly revisit the REPL.
It already behaves nicely (auto-results on expression evaluation, auto-blocks on fn/package/struct/lambda, etc).
It would be nice to have a "reset" feature, so you can reset the REPL session to a specific point, or altogether removing any locals created since the beginning.
It would also be nice to have a "save to file" feature that can persist the code to disk. Perhaps we add a "history"/"recording" feature? This is more of a nostalgia thing from my first language, USL (formerly ASL), but it was incredibly useful!