add link to AGENTS.md in CONTRIBUTING.md

Assisted-by: Claude Sonnet 4.6

Author: MikeGoldsmith

CONTRIBUTING.md

@@ -13,6 +13,8 @@ Before you can contribute, you will need to sign the [Contributor License Agreem
 
 Please also read the [OpenTelemetry Contributor Guide](https://github.com/open-telemetry/community/blob/main/guides/contributor/README.md).
 
+If you are using AI agents to assist with contributions, please read [AGENTS.md](AGENTS.md) for guidance on how to use them responsibly in this project.
+
 # Find your right repo
 
 This is the main repo for OpenTelemetry Python. Nevertheless, there are other repos that are related to this project.