animateToIndex method
Animate to a specific card index (horizontal). Only allowed when verticalProgress == 0.0 (collapsed).
Implementation
void animateToIndex(int index) {
if (verticalProgress > 0.01) return;
final clamped = index.clamp(0, itemCount - 1);
if (clamped != _state.currentIndex) {
_state = _state.copyWith(currentIndex: clamped);
notifyListeners();
}
}