Module pool 

Rayon-backed parallel for: par_for(total, grain, |off, cnt| …).

Replaces the old per-worker Condvar pool with Rayon’s work-stealing scheduler. Same (offset, count) chunk API so all existing call sites (BLAS tiling, SDPA, LayerNorm, …) pick up Rayon without changes.

Functions

num_threads

Total Rayon worker count (configured from [RuntimeConfig::pool_workers]).

par_for

Parallel for: split total items across threads. f(off, cnt) is called once per chunk with disjoint regions.