Variopinta 0.4.4

Variopinta 0.4.4

• Support standard-library pickle for Pipeline and CompiledPipeline,
  preserving execution mode, random sequence position, and shared target/output
  port identities while rebuilding independent native execution state.
• Allow Datasets to own compiled pipelines directly with spawn and forkserver
  workers, without custom serialization or lazy compilation.
• Add an executed Imagenette notebook with augmentation examples, keyed replay,
  and ten epochs of Lightning GPU training using four persistent workers per loader.