Function w4a16_gemv_dual_batch3 

pub fn w4a16_gemv_dual_batch3(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    input: DevicePtr,
    weight0: &QuantizedWeight,
    output0: DevicePtr,
    weight1: &QuantizedWeight,
    output1: DevicePtr,
    n: u32,
    k: u32,
    stream: u64,
) -> Result<()>

2026-09-25: Two NVFP4 GEMVs over the same 3-row input [3, K]; blockIdx.z picks weight0 or weight1, and each writes [3, N].