Function updateBodyFacing

updateBodyFacing(
    facing: BodyFacing,
    targetAngle: number,
    deltaTime: number,
    currentTime: number,
): BodyFacing
Updates body facing direction with smooth rotation

Performs smooth rotation toward target angle at specified speed. Handles:
- Rotation locking during attacks
- 180° turn animation triggering
- Head tracking with independent offset
- Smooth interpolation at 45°/sec
Parameters
- facing: BodyFacing
  Current body facing state
- targetAngle: number
  Desired facing angle in degrees
- deltaTime: number
  Time elapsed since last update in seconds
- currentTime: number
  Current timestamp in milliseconds
Returns BodyFacing
Updated body facing state
Example
```
const facing = createDefaultBodyFacing(0);
const updated = updateBodyFacing(facing, 90, 0.016, Date.now());
// Rotates ~0.72° toward 90° (45°/sec * 0.016s)
```
Korean
몸향하기업데이트
- Defined in systems/animation/systems/BodyFacingSystem.ts:229