Runs the engine-certified parametric-bootstrap likelihood-ratio test
between two nested ML-fitted LMMs through the Rust
mm_bootstrap_lrt_json entry point. The smaller model (fewer estimated
parameters) is the reduced model; the larger is the alternative. The
returned object carries the engine's replicate accounting (successful and
completed replicates, boundary count, Monte-Carlo standard error, seed)
rather than a bare mean() p-value, so every reported number traces back
to a versioned Rust payload.