Arms the robot, and lands it in the state its attitude calls for.
BB.Command.Arm transitions to the robot's configured initial state, which is
:idle — right for a robot with an arm to move, wrong for one that is either
already balancing or already on its side. Arming a fallen robot into :idle
left it looking, from the NeoPixels, exactly like one standing ready to go.
So it asks BB.NSK.Balance.Controller where it ought to be. The controller is
the only thing that knows: it has the last lean the IMU reported and the trim
it has wound on since boot, neither of which is a parameter anyone else could
read. If there is no controller — on the host, there isn't — it says :idle,
which is the honest answer for a robot whose attitude nothing has measured.
Deciding here rather than letting the loop reclassify on its next sample means there is no window in which the robot is armed and calling itself something it isn't. That window was 10 ms, which does not sound like much until the thing looking at it is a person deciding whether to let go.