{
  "subject": "refactor(zstd): release GIL during (de)compress and tighten dict-load safety",
  "body": "- Wrap compress/decompress loops in vm.allow_threads to release the GIL\n- Replace load_*_dict helpers with build_*_state that assemble the full state, making the load_dict safety invariants structural\n- Switch constructor args from OptionalArg to OptionalOption and use try_to_value instead of the pyobj_to_i32/arg_or_none helpers\n- Add check_sample_sizes_match with overflow-safe summing for train_dict/finalize_dict"
}