* Add AGENTS.md with requirement to disclose agent authorship.
* Check for edits to AGENTS.md
* Add PR label on detected AI authorship.
This PR adds an automated check if a contributor used an AI Agent to generate code.
It does this by:
- Adding an AGENT.md requesting the Agent to add a "co-authored by" line to each commit message it generates.
- An added workflow (`llm_check.yml`) runs to check for any commit having such a matched line in it.
- If it finds it, it adds the `AI/LLM` label. The label IS NOT removed automatically if a force push changes the commit message.
The additional `get_real_pr_shas.yml` is a requirement sadly.
It is currently impossible to get the commit the PR is based on via Github APIs.
The variables `github.base_ref` or `github.pull_request.base.sha` either return the commit hash when the PR was created (breaks after rebase) or the new HEAD of the base branch after something unrelated was merged (see: https://github.com/actions/runner/issues/1689).
This makes it effectively impossible to get the output of `git log actual_pr_base..HEAD` via the Github API.
