Function nvfp4_grouped_down 

pub fn nvfp4_grouped_down(
    a: u64,
    packed_ptrs: &[u64],
    sfb_ptrs: &[u64],
    scale2_vals: &[f32],
    c: u64,
    expert_offsets_host: &[i32],
    n: u32,
    k: u32,
    stream: u64,
) -> Result<()>

Single-launch grouped NVFP4 DOWN projection (atlas_cutlass_nvfp4_grouped_down). a is the post-SiLU bf16 intermediate [M_total, K=inter], ALREADY expert-contiguous (no gather). packed_ptrs/sfb_ptrs are device-pointer arrays into the [N=hidden,K/2] packed + swizzled-SFB down tables; scale2_vals and expert_offsets_host are HOST arrays. Writes c [M_total, N=hidden].