I don't think anyone is, or plans to be, watermarking AI-generated code as opposed to text.

[EDITED to add:] As pointed out by a helpful comment below, I was misremembering: Anthropic do apply their watermarking to code, they just say that it will have negligible impact on the actual code (because there's generally less scope for variation in that) but e.g. it will have its usual effect on comments in the code.