Function estimate_normals_aoso_gpu 

pub fn estimate_normals_aoso_gpu(
    runtime: &WgpuRuntime,
    positions: &GpuAoSoXyzBuffer,
    neighbors: &[u32],
    k: u32,
) -> SpatialResult<GpuAoSoNormals>

Estimates normals directly from a retained interleaved XYZ GPU buffer.

neighbors is a global flattened point_count * k index array. Position data remains GPU-resident; only neighbor indices are uploaded. The returned normal buffer stays on the GPU until GpuAoSoNormals::readback is called.