Technically, how does the "every UI action is a commit on a DVCS graph" work? Would every application that is a native étoilé app use this api to construct its UX and document formats? And every app that is not would _not_ have this?

That feels like an ambitious but perhaps misdirected invention of a new paradigm because you'd basically have a native text editor and two other utilities which use it, and then the other five dozen apps would not?

Yeah, strong Xanadu vibes: cool philosophical idea in principle, in practice comes with heavy technical requirements + wouldn't be that useful to 90% of users 90% of the time.