Function fp8_gemm_n128_m128 

pub fn fp8_gemm_n128_m128(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    input: DevicePtr,
    b_fp8: DevicePtr,
    output: DevicePtr,
    m: u32,
    n: u32,
    k: u32,
    stream: u64,
) -> Result<()>

2026-09-25: FP8-weight GEMM with a 128-row CTA (two 64-row chunks); each CTA loads a B tile once for both chunks.