docs(agents): forbid AI-tool attribution in commits & PRs

AGENTS.md

@@ -2,6 +2,10 @@
 
 AI coding assistant context for FastAPI + Next.js Full-Stack Template.
 
+## Git commits & PRs — no AI attribution (hard rule)
+
+Never credit an AI tool as author or co-author of a commit or pull request. Do **not** add `Co-Authored-By:` trailers, "Generated with …" / "Co-authored with …" footers, or `noreply@…` AI author/committer identities — for **any** assistant (Claude, Codex, Gemini, Copilot, Cursor, or otherwise). Commit messages and PR descriptions must read as human-authored, with zero AI tooling credited. Referring to an AI tool as a *subject* (this file, a model id, a CI action) is fine; taking author/co-author credit is not.
+
 ## Quick Start
 
 ```bash