fix: 更新注释并优化通知预制体结构

更新 MissionComp.ts 中的注释说明，明确boss死亡动画后的奖励处理流程
简化 notify.prefab 结构，移除不必要的子节点和组件
更新 slist.prefab 中的资源引用

assets/resources/gui/element/slist.prefab

@@ -167,7 +167,7 @@
       "a": 255
     },
     "_spriteFrame": {
-      "__uuid__": "cb93c900-b440-4571-91d1-7da1636e3d73@7e5cc",
+      "__uuid__": "deedea09-8f2b-400f-9803-4cfd38e45d1a@75b82",
       "__expectedType__": "cc.SpriteFrame"
     },
     "_type": 1,
@@ -183,7 +183,7 @@
     "_isTrimmedMode": true,
     "_useGrayscale": false,
     "_atlas": {
-      "__uuid__": "cb93c900-b440-4571-91d1-7da1636e3d73",
+      "__uuid__": "deedea09-8f2b-400f-9803-4cfd38e45d1a",
       "__expectedType__": "cc.SpriteAtlas"
     },
     "_id": ""