feat(animation): 更新英雄攻击动画并移除默认剪辑

- 将 ha1 和 mo2 英雄的 atk2/atk1 动画重命名为 atk0
- 提高动画采样率从 15/20 到 30，缩短持续时间至 0.667 秒
- 更新动画元数据 UUID 以匹配新资源
- 在 prefab 中移除 _defaultClip 引用，避免默认动画冲突

assets/resources/game/heros/hero/mo2/atk2.anim.meta

@@ -1 +1,13 @@
-{"ver":"2.0.3","importer":"animation-clip","imported":true,"uuid":"74fccdd7-c5d3-4f9c-bc29-4e17d8f181e1","files":[".cconb"],"subMetas":{},"userData":{"name":"atk2"}}
+{
+  "ver": "2.0.3",
+  "importer": "animation-clip",
+  "imported": true,
+  "uuid": "1f1f9e83-4e0a-43fd-ab0b-bd260e793cbb",
+  "files": [
+    ".cconb"
+  ],
+  "subMetas": {},
+  "userData": {
+    "name": "atk2"
+  }
+}