Handling AI contributions

[ann0see]

Currently, we have a bunch of AI contributions and is hard to triage them.

Many are still useful - however I believe there is still some stuff that might be sloppy.

We need to get a policy on what to accept and what not in CONTRIBUTING.md. Especially, there needs to be a discussion on how to handle those new PRs. I've opened a PR to add AGENTS.md: #3785 which might be tweaked to tell AI models on what is allowed and what isn't.

My personal stance is that we should not ban AI contributions. However we need to ensure that there's no slop.

Suggestions:

1. The contributor must know and be able to reason about the code. Otherwise, we may close the PR immediately
2. A contributor must AI review and then self-review before opening the PR
3. A contributor should mention if/which AI model was used
4. Maintainers should tag those PRs as AI generated with the respective tag.

[mcfnord]

You might get a new PR, and your first move might be to ask your AI to review it. I'm not sure it matters where it came from.

We don't have the institutional knowledge yet to understand the pitfalls or the opportunities. I hope everyone can immerse themselves for a few days, learn some core skills, like changing models and effort levels. A contributor does need to notice and fix some common failures, like successfully integrating new information into the existing work (good citizenship).

Push an AGENTS.md into the repo (into both repos). That will go a long way addressing the most obvious failure patterns, which I wouldn't describe as slop (a term that I don't think is so useful). I bet the core problems are: a PR does something we don't do, in a way we don't do it, or can't practically review, or prefer to consider in pieces rather than all at once. I bet AGENTS.md can reduce all of those problems.