Function kda_decode_token 

pub fn kda_decode_token(
    x_qkv: &[f32],
    conv_w: &[f32],
    gate: &[f32],
    beta: &[f32],
    cfg: &KdaConfig,
    state: &mut KdaState,
) -> Vec<f32>

One decode token: conv update then recurrent step.