Function sampleobservation_replicates 

pub fn sampleobservation_replicates<R: Rng + ?Sized>(
    spec: &GenerativeSpec,
    n_draws: usize,
    rng: &mut R,
) -> Result<Array2<f64>, EstimationError>

Collect multiple synthetic replicates into an n_draws × nobs matrix.

This is intentionally the allocating convenience surface. Streaming consumers should call sampleobservation_replicate_chunks directly.