euler_to_quat(roll: float, pitch: float, yaw: float) -> tuple[float, float, float, float]
Convert Roll-Pitch-Yaw (XYZ intrinsic) to quaternion (x, y, z, w). Angles in radians.
quat_to_euler(x: float, y: float, z: float, w: float) -> tuple[float, float, float]
Convert quaternion (x, y, z, w) to Roll-Pitch-Yaw (XYZ intrinsic). Returns (roll, pitch, yaw) in radians.