Function decode_descriptors 

pub fn decode_descriptors(
    buf: &[u8],
) -> Result<(GlobalMetadata, Vec<DataObjectDescriptor>), TensogramError>

Decode global metadata and per-object descriptors without decoding any payload data.

This is cheaper than decode because the pipeline (decompression, filter reversal, endian swap) is never executed. Use it when you only need shapes, dtypes, and metadata — e.g. for building xarray Datasets at open time.