FP8 arithmetic

Quantizing value residuals and casting softmax to FP8 speeds Nunchux's attention kernel 1.46x on an H200

The September 14th VC-Attention paper reports 1.46x on an H200 and 1.59x on a B200 against BF16 FlashAttention-4, measured at the attention call. How much of that reaches a finished clip depends on how much of your step is attention.