More consistent dependency tracking and more!

I generally cleaned up a lot of the jank from my rush to get an MVP working. Big thing is I actually have a somewhat working “timeline” now so each feature saves its output and it doesn’t get overwritten by the next one. Also added a new feature called “Script” which is sort of a back-up feature which allows you to inject arbitrary build123d code into the project and build off of it. This allowed me to remove the code editor along with the weird code to deal with manual code generation that wasn’t a feature.

Overall, much less buggy experience and stuff working!