AI tooling must be disclosed for contributions (#8289)

I think, at this stage of AI, it is a common courtesy to disclose this. 

In a perfect world, AI assistance would produce equal or higher quality
work than any human. That isn't the world we live in today, and in many
cases it's generating slop. I say this despite being a fan of and using
them successfully myself (with heavy supervision)! I think the major
issue is **inexperienced human drivers of AI** that aren't able to
**adequately review their generated code.** As a result, they're pull
requesting code that I'm sure they would be ashamed of if they knew how
bad it was.

The disclosure is to help maintainers assess how much attention to give
a PR. While we aren't obligated to in any way, I try to assist
inexperienced contributors and coach them to the finish line, because
getting a PR accepted is an achievement to be proud of. But if it's just
an AI on the other side, I don't need to put in this effort, and it's
rude to trick me into doing so.

**I'm a fan of AI assistance and use AI tooling myself.** But, we need
to be responsible about what we're using it for and respectful to the
humans on the other side that may have to review or maintain this code.

(In the spirit of this PR... none of this PR was AI generated. lol.)

Author: mitchellh

CONTRIBUTING.md

@@ -13,6 +13,40 @@ we can always convert that to an issue later.
 > time to fixing bugs, maintaining features, and reviewing code, I do kindly
 > ask you spend a few minutes reading this document. Thank you. ❤️
 
+## AI Assistance Notice
+
+> [!IMPORTANT]
+>
+> If you are using **any kind of AI assistance** to contribute to Ghostty,
+> it must be disclosed in the pull request.
+
+If you are using any kind of AI assistance while contributing to Ghostty,
+**this must be disclosed in the pull request**, along with the extent to
+which AI assistance was used (e.g. docs only vs. code generation).
+If PR responses are being generated by an AI, disclose that as well.
+As a small exception, trivial tab-completion doesn't need to be disclosed,
+so long as it is limited to single keywords or short phrases.
+
+An example disclosure:
+
+> This PR was written primarily by Claude Code.
+
+Or a more detailed disclosure:
+
+> I consulted ChatGPT to understand the codebase but the solution
+> was fully authored manually by myself.
+
+Failure to disclose this is first and foremost rude to the human operators
+on the other end of the pull request, but it also makes it difficult to
+determine how much scrutiny to apply to the contribution.
+
+In a perfect world, AI assistance would produce equal or higher quality
+work than any human. That isn't the world we live in today, and in most cases
+it's generating slop. I say this despite being a fan of and using them
+successfully myself (with heavy supervision)!
+
+Please be respectful to maintainers and disclose AI assistance.
+
 ## Quick Guide
 
 **I'd like to contribute!**