Of course exceptions apply. Some basic information that will reliably be discovered is still worth adding to your AGENTS.md to cut down on token use. But after a couple obvious things you quickly get into the realm of premature optimization (unless you actually measure the effects)
If you find any, consider making them into skills or /commands or maybe even add them to AGENTS.md.
Is it by characters human typed vs AI generated, or by commit or something?
Cursor dashboard. I know they're incentivized to over-estimate but feels directionally accurate when I look at recent PRs.
Don’t really think about it. I think when I talk to it through Slack, cursor users codex, in my ide looks like it’s whatever highest claude. In Github comments, who even knows