Function qwen4_exp_gen_once 

pub(crate) fn qwen4_exp_gen_once(
    gpu: &mut Gpu<'_>,
    cpu: Option<&CpuModel<'_>>,
    cpu_state: Option<&mut State>,
    tok: &ChatTokenizer,
    ids: &[u32],
    max_tokens: usize,
    options: &Options,
    resume: Option<PrefillResume>,
    emit: &mut dyn FnMut(u32) -> Result<()>,
) -> Result<()>