Function w8a16_gemm 

pub fn w8a16_gemm(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    input: DevicePtr,
    weight: DevicePtr,
    block_scale: DevicePtr,
    output: DevicePtr,
    m: u32,
    n: u32,
    k: u32,
    stream: u64,
) -> Result<()>

2026-09-25: W8A16 GEMM for M>1: C[M,N] = A[M,K] @ dequant(B[N,K])^T, with the 2D block scale [ceil(N/128), ceil(K/128)] FP32.