interdisciplinary Phd programs in philosophy and computer science (AI, ML)?
I suggest that you don't need a "program" but rather a school and a professor who is willing to be flexible and let you take the lead in large part. Maybe a couple of advisors in different fields. I think there are a lot of top institutions that can afford such flexibility and Stanford is likely one of them. But you should probably pursue this individually and in person. 

I'll note that doctoral programs are normally pretty individualized in any case, and often a student needs to take a lead if the topic is not completely within the expertise of the advisor.