tal: make stopping for idling more precise

[nyiyui]

Currently, idling means changing power to a set value. However, this means the train does not stop in time (e.g. due to 滑走) and some trains do not stop at all due to having more sensitive motors.

• change idling to apply brakes → idle power.
• ignore current detection from soyuu-line if the power applied to the domain/line is 0