mixle.stats.latent._hidden_markov_numba_kernels module

Shared numba Baum-Welch / forward kernels for the HMM family.

These forward-backward kernels are byte-for-byte identical across the HMM variants (hidden_markov and look_back_hmm). They are consolidated here so the numba JIT compiles and caches them once and the variants share the same cache=True object code.