Interface I3mfSerializer<T>

Minimal contract for a 3MF serializer that can stream its output through a sink callback.

The sink callback receives:

• err: any error produced by the serialization pipeline (if any)
• chunk: a chunk of bytes to append to the destination
• final: true when this is the last chunk

Important:

• Implementations should call sink with final=true exactly once, or rely on the underlying zip lib to do so.
• Consumers may ignore final if they just buffer everything.