add LLM use policy and contributing guide

[grgmiller]

Purpose

Adds a markdown file that provides instructions to LLM models on how to assist with code changes in this repo.

The main question for reviewers is: should we include this in a public repo? There is nothing private/sensitive in the file (it is all derived from the codebase itself), but we just haven't established a policy for this yet.

Also updates the README with a LLM use policy and the PR template

[brandonwang15]

lgtm

Separately though, I wonder if, since this is public, should we eventually include a note in our README about our own norms/principles around writing and reviewing AI-generated/assisted code?

We probably require more internal discussion / thought to figure out what that is ourselves, and how we want to present that, but it might be a good thing to have clarity on for something public-facing.

Also PRs are public on this repo too, just FYI, so fwiw this is technically visible already

[grgmiller]

@brandonwang15 do you think that we want to add any AI principles to this repo, like: https://github.com/catalyst-cooperative/pudl?tab=contributing-ov-file#llm-use-policy?

I think as written, this file also provides relevant design standards for contributing to this repo whether you are an LLM or a human. Would it make sense to rename this to a "CONTRIBUTING.md" file so that it is less tied to Claude specifically (but if using an LLM, you could point it to this file to understand how to contribute)?

[brandonwang15]

@brandonwang15 do you think that we want to add any AI principles to this repo, like: https://github.com/catalyst-cooperative/pudl?tab=contributing-ov-file#llm-use-policy?

I think as written, this file also provides relevant design standards for contributing to this repo whether you are an LLM or a human. Would it make sense to rename this to a "CONTRIBUTING.md" file so that it is less tied to Claude specifically (but if using an LLM, you could point it to this file to understand how to contribute)?

I'd be pro adding something like that, I like the PUDL writeup. And yeah renaming CONTRIBUTING.md makes sense to me.

[grgmiller]

@brandonwang15 @sarahchute I made some updates based on your feedback, adding an LLM policy (copied from PUDL), and a section to the PR template to describe LLM use. I also renamed the file CONTRIBUTING.md instead of CLAUDE.md