Given it’s a controversial subject I personally back your original request which would serve the part of the community that is, at present, more on the sceptical side (fair enough)
However I suspect that we would end up labelling almost everything, which kind of defeats the point?
I would also agree with others that not all AI generated code is equal - some of it is written by more recent, more expensive models, guided by experienced developers, whereas in other cases it might be a one-shot from a less experienced person using a less capable model and the repo might not be utilising best practice - and you can only judge that by examining the repo itself and also observing if people are having frequent issues.