ExtendedModelResponse

Model response with an optional 'Command' from 'wrap_model_call' middleware.

Use this to return a 'Command' alongside the model response from a 'wrap_model_call' handler. The command is applied as an additional state update after the model node completes, using the graph's reducers (e.g. 'add_messages' for the 'messages' key).

Because each 'Command' is applied through the reducer, messages in the command are added alongside the model response messages rather than replacing them. For non-reducer state fields, later commands overwrite earlier ones (outermost middleware wins over inner).