Review noted "For CUDA, SM89+ is required. For ROCm, MI300/MI350 is required."

The predicate already encodes exactly that: is_sm_at_least_89() short-circuits
on torch.version.cuda and is_MI300()/is_MI350() short-circuit on torch.version.hip,
so only one arm can be true for a given build. Only the message was ambiguous,
so make both backend requirements explicit.