TurboQuant KV Cache Optimization

Lloyd-Max codebook quantization for LLM KV caches. 3-bit (turbo3) and 4-bit (turbo4) with FWHT rotation and norm correction. Beats q8_0 quality at 3-5x compression. Research focus: closing the head_dim=128 quality gap, decode speed on MoE models, and exploring CAT/SQuat/InnerQ techniques.