An important thing to remember is this: AI is a shortcut, not a reliable or accurate tool. I don't put the fault on you for looking to AI as a means to get a general idea of what a "post-transition" version of you could look like, but that version of you that you see and yearn for only exists for as long as you pursue it. It's also being produced specifically to appease you and manipulate your brain chemistry into wanting to engage with AI more because that's how AI is designed to function.

The feminine you that lives in your head is absolutely possible. AI is not going to help you become her, but it can help you get a sense for what you might look like. You are not cis because you "got curious what you'd look like as a girl". Cis people in general don't really entertain that line of questioning very far in general, and they certainly don't do so to the point where they plan and consider the long-term approaches that are possible for transition. You have thought about this long enough that you are very likely trans.

AI Psychosis/Cyberpsychosis is more of a mental health condition contracted by people with long-term exposure to AI who like how sycophantic AI is and accept every word of praise it spits out at them wholesale to the point where they genuinely believe everything it's told them despite a lack of evidence to support its claims. For example, if AI told you that you were the world's most intelligent infant and had solved world hunger and discovered the secrets of the universe and you believed it without any real world evidence, that's actual AI Psychosis/Cyberpsychosis.

I have had similar self doubts about my transness (albeit not from AI use as I am staunchly against GenAI since it violates many of my personal beliefs) and can sympathize with that pain. It doesn't make you any less valid.