fix: make simd module public (was pub(crate)) Consumers (bgz-tensor, thinking-engine) need ndarray::simd::bf16_to_f32_batch and other polyfill exports. Was incorrectly restricted to pub(crate). https://claude.ai/code/session_01ChLvBfpJS8dQhHxRD4pYNp

fix: make simd module public (was pub(crate)) Consumers (bgz-tensor, thinking-engine) need ndarray::simd::bf16_to_f32_batch and other polyfill exports. Was incorrectly restricted to pub(crate). https://claude.ai/code/session_01ChLvBfpJS8dQhHxRD4pYNp #129