I guess that gets to my question a little more - I can see them being helpful for reviewing. Do you go back to them after the review?

I work in data and machine learning, it's pretty common to attach artifacts like charts, images, data outputs to a PR for me, but not include them in the codebase.

I'd only want to do that if it was going to be useful at some future point - do you go back to chats / transcripts etc months after a PR is merged to understand its design? (that sounds rhetorical, but I promise it's a genuine question!)