Function build_voxel_segments_gpu_from_keys_buffer 

pub fn build_voxel_segments_gpu_from_keys_buffer(
    runtime: &WgpuRuntime,
    keys_buffer: &Buffer,
    point_count: u32,
    padded_count: u32,
) -> SpatialResult<GpuVoxelSegments>

Builds GPU-resident voxel segments from a GPU keys buffer.