Function py_poisson_simulate 

fn py_poisson_simulate<'py>(
    py: Python<'py>,
    rate_hz: f64,
    dt_ms: f64,
    rng_state: u16,
    n_steps: usize,
    rate_override: f64,
) -> PyResult<(Bound<'py, PyArray1<u8>>, u16)>

Full-contract homogeneous-Poisson batch with the canonical LFSR16 trial.