chore: disable grid center sphere and fix priority

thermion_dart/native/include/scene/GridOverlay.hpp

@@ -44,7 +44,7 @@ public:
     size_t getInstanceCount() override { return _instances.size(); }
     SceneAsset* getInstanceByEntity(utils::Entity entity) override;
     SceneAsset* getInstanceAt(size_t index) override;
-    size_t getChildEntityCount() override { return 2; }
+    size_t getChildEntityCount() override;
     const Entity* getChildEntities() override;
     Entity findEntityByName(const char* name) override;