Some sort of LLM audit trail is needed (containing prompts used, model identifier and marking all code written by LLM). It could be even signed by LLM providers (but that wouldn't work with local models). Append only standard format that is required to be included in PR. It wouldn't be perfect (e.g. deleting the log completely), but it might help with code reviews.
This would probably be more useful to help you see what (and how) was written by LLMs. Not really to catch bad actors trying to hide LLM use.
This would be a useful feature to bake into the commits generated by agents. Heck you don’t even need to wait — just change your prompt to tell it to include more context in its commit messages and to sign them as Claude rather than yourself…