fix: Camera.main→GameObject.Find(Main Camera) 解决摄像机不同步

根因: Camera.main在SwitchToCamera2禁用主摄像机后返回null,
PlayOpeningFlow/ReturnToHome无法重新启用主摄像机。
全部改用GameObject.Find("Main Camera")按名字查找。

Assets/Scripts/UI/PageController.cs

@@ -362,13 +362,11 @@ public class PageController : MonoBehaviour
     {
         Debug.Log("PageController: [ReturnToHome] 返回首页并重置场景");
 
-        // 恢复 man 和 man2
         var man = GameObject.Find("man");
         if (man != null) man.SetActive(true);
         var man2 = GameObject.Find("man2");
         if (man2 != null) man2.SetActive(true);
 
-        // 隐藏实验专用物件
         var woman = GameObject.Find("woman");
         if (woman != null) woman.SetActive(false);
         var manInjury = GameObject.Find("manInjury");
@@ -376,13 +374,12 @@ public class PageController : MonoBehaviour
         var medicalBox = GameObject.Find("medicalBox");
         if (medicalBox != null) medicalBox.SetActive(false);
 
-        // 恢复主摄像机
-        var mainCam = Camera.main;
-        if (mainCam != null) mainCam.enabled = true;
-        var cam2 = GameObject.Find("camera2");
-        if (cam2 != null) { var c = cam2.GetComponent<Camera>(); if (c != null) c.enabled = false; }
+        // 用名字找主摄像机（Camera.main 在禁用后返回 null）
+        var mainGo = GameObject.Find("Main Camera");
+        if (mainGo != null) { var c = mainGo.GetComponent<Camera>(); if (c != null) c.enabled = true; }
+        var cam2Go = GameObject.Find("camera2");
+        if (cam2Go != null) { var c = cam2Go.GetComponent<Camera>(); if (c != null) c.enabled = false; }
 
-        // 重置 Animator 参数
         var manAnim = man != null ? man.GetComponent<Animator>() : null;
         if (manAnim != null) { manAnim.SetBool("IsStart", false); manAnim.SetBool("IsFull", false); }