Replace dedicated strafe/run-left/right animations with plain walk/run
plus a SpineLow bone yaw twist driven by the difference between travel
heading and camera facing. Adds setInstanceTorsoYaw() and a travelYaw
tracker in CameraController.
Camera smoothing now snaps 1:1 while actively dragging or keyboard
turning instead of always lerping, reducing perceived input lag.
Mounts use MOUNT_RUN_LEFT/RIGHT animations for strafing when available.
Default mouse invert changed to off.