Function w4a16_gemv_dual 

pub fn w4a16_gemv_dual(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    input: DevicePtr,
    weight1: &QuantizedWeight,
    output1: DevicePtr,
    weight2: &QuantizedWeight,
    output2: DevicePtr,
    n: u32,
    k: u32,
    stream: u64,
) -> Result<()>

2026-09-25: Two W4A16 GEMVs over the same BF16 input in one launch; blockIdx.z picks weight1 or weight2. Both projections have n outputs.