Fix issues with puzzle loading order and add saving state when using Menu

Assets/Scripts/PuzzleS/PuzzleManager.cs

@@ -50,7 +50,24 @@ namespace PuzzleS
 
         // Save system configuration
         public override bool AutoRegisterForSave => true;
-        public override string SaveId => $"{SceneManager.GetActiveScene().name}/PuzzleManager";
+        
+        /// <summary>
+        /// SaveId uses CurrentGameplayScene instead of GetActiveScene() because PuzzleManager
+        /// lives in DontDestroyOnLoad and needs to save/load data per-scene.
+        /// </summary>
+        public override string SaveId
+        {
+            get
+            {
+                string sceneName = SceneManagerService.Instance?.CurrentGameplayScene;
+                if (string.IsNullOrEmpty(sceneName))
+                {
+                    // Fallback during early initialization
+                    sceneName = SceneManager.GetActiveScene().name;
+                }
+                return $"{sceneName}/PuzzleManager";
+            }
+        }
         
         /// <summary>
         /// Singleton instance of the PuzzleManager.
@@ -602,7 +619,8 @@ namespace PuzzleS
                 // Update any behaviors that registered before RestoreState was called
                 foreach (var behaviour in _pendingRegistrations)
                 {
-                    UpdateStepState(behaviour);
+                    if(behaviour != null)
+                        UpdateStepState(behaviour);
                 }
                 _pendingRegistrations.Clear();
             }