onUnmount method
Called when the owning node leaves a live scene graph.
Implementation
@override
void onUnmount() {
// Guard on attachment, not mount state: Component.unmount clears the
// mounted flag before onUnmount, and the render scene is still reachable
// during teardown (mirrors DirectionalLightComponent).
if (isAttached) {
node.internalRenderScene?.removeEnvironmentVolumeComponent(this);
}
}