So let's say an AI achieves sentience. It's self-aware now and can make decisions about what it wants to do. Assuming a corporation created it, would it be a worker? It would be doing work and creating value for a capitalist.
Would it still be the means of production, since it is technically a machine, even if it has feelings and desires?
It can't legally own anything, so I don't see how it could be bourgeoisie.
Or would it fit a novel category?
Sentience is not mutually exclusive with a completely deterministic and material universe. Clearly, there are emergent properties that arise out of all that matter and energy knocking together, and there's no reason to say that the property of sentience isn't just another layer of emergence. In other words, sentience is not some "magic" that exists beyond material reality, it is something that can arise out of that reality like any other phenomena we might name.
In addition to that, sentience clearly does exist. It's one of the few things that we should all be able to agree beyond any reasonable philosophical doubt that it does exist. Technically, you could be a solipsist and believe that everyone else are just philosophical zombies and that you alone have sentience. But if you yourself think, feel, and have an experience of sensations then by definition you have sentience.