Shrink the non-grouped (dense/attention) DeepGEMM warmup M grid by attn_cp_size under NSA prefill in-seq CP (per-rank M = tokens/cp), while keeping the grouped MoE GEMM grid full (deepep all-to-all re-gathers all tokens; topk==ep_size keeps MoE M ~= chunked). Gated by _cp_dense_warmup_divisor.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
(cherry picked from commit 672ef3a6609abd100e5e95b42016d17d0a2966e5)