Add a reasoning effort to system message in droid exec stream-json mode

[britannio]

Hey, I'm adding droid to Vibe Kanban (BloopAI/vibe-kanban#1057) and a minor improvement would be if the resolved reasoning effort were outputted in the system message as is done with the selected model.
My understanding is that the valid values to provide to the cli are none, dynamic, off, low, medium, high, but presumably some models will ignore it.

Thanks.

[factory-ben]

noted! will notify the team cc @factory-tianwei @varin-nair-factory