Function sigmoid_blend_device 

pub fn sigmoid_blend_device(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    output: DevicePtr,
    src: DevicePtr,
    gate_ptr: DevicePtr,
    num_elements: u32,
    stream: u64,
) -> Result<()>

2026-09-25: output[i] += sigmoid(*gate_ptr) * src[i], where gate_ptr is one BF16 scalar in device memory (bf16_sigmoid_blend_device in kernels/gb10/common/residual_add.cu).