Preserve motor power sign in reverse operation

[rhorvath02]

Finding

The power-limited motor used a nonnegative shaft-speed magnitude to convert requested power into torque. In reverse rotation this made positive motoring power produce the wrong torque sign, and similarly inverted reverse regenerative operation.

Fix

Preserve shaft-speed sign when converting limited mechanical power to torque, expose a configurable low-speed regularization power, and give the torque actuator an explicit fixed zero start value.

Validation

• Focused regression passed for forward/reverse motoring, forward/reverse regeneration, and both launch directions.
• At 0.01 s, reverse motoring is +9345.616 W / -94.090 Nm; reverse regeneration is -10645.089 W / +107.173 Nm.
• Full VehicleSim reached QSS at the baseline 6.049508 s with the same solver counts; the previous under-specified tau_act initialization warning is gone.