Function moe_expert_silu_down_shared_prefill 

pub fn moe_expert_silu_down_shared_prefill(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    gate_out: DevicePtr,
    up_out: DevicePtr,
    packed_ptrs: DevicePtr,
    scale_ptrs: DevicePtr,
    scale2_vals: DevicePtr,
    output: DevicePtr,
    expert_indices: DevicePtr,
    sh_gate_in: DevicePtr,
    sh_up_in: DevicePtr,
    sh_down: &QuantizedWeight,
    sh_down_out: DevicePtr,
    n: u32,
    k: u32,
    top_k: u32,
    num_tokens: u32,
    stream: u64,
) -> Result<()>

2026-09-25: SiLU(gate) * up, then the down GEMV, for the routed and shared rows of moe_expert_gate_up_shared_prefill, with the same row split. Routed rows read gate_out/up_out and write output ([num_tokens * top_k, n] BF16); shared rows read sh_gate_in/sh_up_in and write sh_down_out ([num_tokens, n] BF16).