Variable BACKWARD_RETREAT_ANIMATIONConst

Backward retreat animation (뒤로 물러서기)

Coordinated leg backpedaling with defensive posture.

Animation phases:

1. Push back (0.0s): Back foot plants, front foot lifts
2. Slide (0.2s): Smooth backward movement
3. Plant (0.35s): Front foot plants
4. Reset (0.45s): Return to guard stance

Duration: 450ms