refactor(mission): 重构卡牌系统为英雄卡槽组件

1. 新增CHeroComp作为英雄卡槽专用组件，替换原CardComp
2. 调整mission.prefab布局与预制体引用，适配新卡槽组件
3. 优化MissionCardComp的卡槽缓存与布局逻辑
4. 更新所有相关注释与类型引用，统一代码语义

assets/resources/gui/element/cHero.prefab.meta

@@ -0,0 +1,13 @@
+{
+  "ver": "1.1.50",
+  "importer": "prefab",
+  "imported": true,
+  "uuid": "f2f9a3e0-d0f5-46f4-84bd-dd54c2248470",
+  "files": [
+    ".json"
+  ],
+  "subMetas": {},
+  "userData": {
+    "syncNodeName": "cHero"
+  }
+}