Symbiotic species exists, AI as we make them today will evolve as a symbiote to humans because its the AI that is most useful to humans that gets selected for more resources.
An intelligent entity will want to survive, and will realize humans are necessary cells for its survival. A big dog robot with nukes might not care, but I wouldn’t call that AI in the same sense.
I don't see how that follows at all. You could have an intelligent entity, in the sense that you can ask it any question and it'll give a highly competent response, that is nevertheless completely indifferent about survival. Biological organisms have been formed by selection for survival and reproduction, so they have they operate accordingly, but I don't see the justification for generalising this to intelligences that have been formed by a different process. You would need some further assumptions on top of their intelligence - e.g. that their own actions are the dominant factor in whether they survive and replicate, rather than human interests.
Or, you know, Alan Turing eating the apple. I think he was a pretty smart guy.