对 #978 的回复: 密集模型 CPU 性能差距与上游 LLaMA.cpp

**Follow-up to PR #978** (which resolves #975 — CPU flash-attention regression). PR #978 fixes the CPU-FA regression on MoE models (beats upstream on Qwen3-30B-A3B-Q4_K_M by +12% pp / +3% tg on Xeon Gold 6338 with `-fa on`). On the dense **LLaMA-3.1-8B-Instruct-Q4_K_M** reproducer from #975, however, our build still trails upstream by ~22% pp and ~7% tg — and the gap is present *equally with `-fa on` and `-fa off`*, so it's not FA-related.