Function sample_boundary_token 

pub fn sample_boundary_token(
    e: &Engine,
    logits: &[f32],
    sp: &SpecSampling,
    pen_hist: &[u32],
    sctr: &mut u32,
    site: &str,
) -> Result<u32, Box<dyn Error>>

Host-row twin of sample_boundary_token_dev (the prime / feed / entry rows arrive as host Vec<f32>).