what about using git notes to stash the summaries? (https://git-scm.com/docs/git-notes)

Very similar for me. I have a plans folder in my root where I store the plans while they're either under improvement or under implementation. Once they're done they're moved into the plans/old folder. So far it's worked great. It's a couple of manual steps extra but very helpful record.

Pretty much the same thing. I don't find it to be a burden. Regarding the product, I'm willing to believe I just don't see big picture, but without some peek at the magic, I don't know how much easier this could really be.

[dead]