handlePointerDelta method
Applies a mouse pointer delta (in logical pixels) as camera rotation.
Sign convention matches HeadTracker.applyTouchDelta (grab-the-world drag): dragging right rotates the view left.
Implementation
void handlePointerDelta(Offset delta) {
if (!enabled) return;
final dy = invertY ? delta.dy : -delta.dy;
cameraRig.rotate(-delta.dx * lookSensitivity, dy * lookSensitivity);
}