Function py_evo_batch_mutate 

pub(crate) fn py_evo_batch_mutate(
    _py: Python<'_>,
    genomes: Vec<Vec<f64>>,
    mutation_rate: f64,
    mutation_scale: f64,
    seed: u64,
) -> Vec<Vec<f64>>

Batch-mutate population weights (Rust-accelerated).