feat: 上一步/下一步支持woman步进撤销重做

- StepManager新增自由步进模式(无Config时):
  InitWomanSteps/RecordWomanStep/WomanStepPrevious/WomanStepNext
- PreviousStep/NextStep在_activeSteps为null时走woman步进
- TouchPositionHandler点击后通知StepManager.RecordWomanStep
- PageController在实验启动时调用InitWomanSteps初始化
- 上一步→woman回到上个位置+显示对应touchPoint
- 下一步→woman移到下个位置+显示对应touchPoint

Assets/Scripts/Interaction/TouchPositionHandler.cs

@@ -39,6 +39,11 @@ public class TouchPositionHandler : MonoBehaviour
             Debug.Log($"[TouchPosition] woman 移动到 {targetPosition.name}");
         }
 
+        // 通知 StepManager 记录步骤
+        int stepIndex = transform.GetSiblingIndex() + 1;
+        var sm = FindObjectOfType<StepManager>();
+        if (sm != null) sm.RecordWomanStep(stepIndex);
+
         StopAllCoroutines();
         if (_meshRenderer != null) _meshRenderer.enabled = false;