CONTRIBUTING: add policy on use of LLMs / "generative AI".

Author: whitequark

CONTRIBUTING.txt

@@ -8,6 +8,17 @@ See the "Contributing" section of the documentation manual for more details
 about contributing to Amaranth.
 
 
+USE OF LARGE LANGUAGE MODELS / "GENERATIVE AI" TOOLS
+
+Contributions created using large language models or "generative AI" tools are
+not accepted.
+
+The burden of ensuring the appropriateness of a contribution lies on its
+author, with code review being a tool to assist this process, and even partial
+shift of this responsibility to reviewers that occurs when these tools are
+used is both unethical and unsustainable.
+
+
 COPYRIGHTS and LICENSE
 
 Amaranth HDL is licensed under the 2-clause BSD license, which is contained in