Provide instructions for external contributors using AI

[MikeMcC399]

What would you like?

Define the rules for AI use in PRs:

• Do PRs need to declare that AI was used?
• Does a submitter who used AI need to declare that they understand the code they have submitted / changed?
• Do PRs need to use the Cypress PR template or can they replace them with an AI-generated template?

https://github.com/zulip/zulip/blob/main/CONTRIBUTING.md#ai-use-policy-and-guidelines gives an example of what another repo has set up as guidelines (published on https://zulip.readthedocs.io/en/latest/contributing/contributing.html#ai-use-policy-and-guidelines).

Why is this needed?

Related to PR #33429 there's a need to have an update to the CONTRIBUTING instructions for contributors using AI to submit PRs.

Adding AGENTS and CLAUDE implies that there is an expectation that AI-aided PRs will be submitted, so this is also my assumption, that external contributors may use AI for PRs.

cc: @ryanthemanuel

[jennifer-shehane]

@MikeMcC399 Thanks for bringing this up, we're internally thinking through guidance here.

[MikeMcC399]

GitHub has announced some changes that are intended to ease handling PRs generated by AI, however I don't see anything yet that will significantly help. See Welcome to the Eternal September of open source. Here’s what we plan to do for maintainers.

The Node.js organization is also in the process of formulating some contributing rules and in general open source repos are on a steep learning curve related to handling AI-aided submission.

[MikeMcC399]

#33463 would close this issue