It's not, to be fair.

> I use my own `.md` plan files rather than Claude Code’s built-in plan mode. The built-in plan mode sucks.

From Claude docs: Planning is most useful when you’re uncertain about the approach, when the change modifies multiple files, or when you’re unfamiliar with the code being modified. If this isn't true, skip the plan.

Can you easily version their plans using git?

"Write plan to the plans folder in the project"

Can that be saved somewhere so it's done for every session?

You can just read the docs man