/// Compress `data` to a base64-encoded gzip string.
///
/// Delegates to the boundary-layer implementation in `checkpoint::io::compression`,
/// which owns all I/O state (encoder, buffers).
/// Decompress a base64-encoded gzip string back to UTF-8.
///
/// Delegates to the boundary-layer implementation in `checkpoint::io::compression`,
/// which owns all I/O state (decoder, buffers) and enforces the size cap.