track_insert_key() returns -1 (error) when using Quaternion values
on TYPE_ROTATION (type=1) tracks in Godot 4.2.1.
The correct format is: add_track(1) + track_insert_key(track, time, Vector3(euler))
This applies to both Walk/Run/Jump/Idle animations - all must use
Vector3 euler angles for rotation keyframes.