pub fn k64_n64_kernel(gpu: &dyn GpuBackend) -> KernelHandleExpand description
2026-09-25: The N_TILE=64 deep-K twin w4a16_gemm_t_k64_n64_p3.
KernelHandle(0) when the target lacks it, or, with no lookup, when
METRALE_NO_K64_N64 is set to any value (0 included).