Host adapter for active subprocess control.
Hosts own the actual process model. The shared runner only requires an adapter seam so later CLI-dispatch implementations can thread host context, provenance, and budget state through process startup and interruption.
Summary
Callbacks
@callback clear_active(WorkflowStem.Types.execution_id()) :: :ok | {:error, term()}
@callback halt_active(WorkflowStem.Types.execution_id(), term(), map()) :: :ok | {:error, term()}
@callback register_active(WorkflowStem.Types.execution_id(), term(), map()) :: :ok | {:error, term()}