Function serialize_batch_with_layout 

pub fn serialize_batch_with_layout(
    meshes: &[MeshData],
    layout: ParquetLayout,
) -> Result<Bytes, ParquetError>

Serialize one batch under the layout the client asked for, sharing nothing.

The batch-local streaming route’s per-batch blobs: SharedShapes here means only that the mesh table carries identity rot0..rot8, since each blob must decode on its own. Sharing across batches is the cross-batch stream’s, planned by parquet_stream_shapes::StreamShapePlanner (#5407).