Function moe_expert_down_act_bf16_grouped 

pub fn moe_expert_down_act_bf16_grouped(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    act: DevicePtr,
    down_ptrs: DevicePtr,
    output: DevicePtr,
    expert_offsets: DevicePtr,
    active_experts: DevicePtr,
    active_count: DevicePtr,
    sh_act: DevicePtr,
    sh_down: DevicePtr,
    sh_down_out: DevicePtr,
    n: u32,
    k: u32,
    cap: u32,
    num_tokens: u32,
    stream: u64,
) -> Result<()>

2026-10-02: Grouped BF16 down over the hi + lo SiLU rows. k is the intermediate width; rows of act and output are sorted positions, rows of sh_act and sh_down_out tokens.