fix(英雄): 调整近战最小攻击距离并修复攻击动画循环

- 将 meleeMinEnemyDistanceX 从 80 减少到 60，优化近战英雄攻击距离判定
- 在 HeroAnmComp 中添加 _atkIndex 变量，实现 atk0、atk1、atk2 攻击动画的循环播放

assets/script/game/hero/MoveComp.ts

@@ -37,7 +37,7 @@ interface MoveFacConfig {
 @ecs.register('MoveSystem')
 export class MoveSystem extends ecs.ComblockSystem implements ecs.ISystemUpdate {
     private readonly meleeAttackRange = HeroDisVal[HType.Melee];
-    private readonly meleeMinEnemyDistanceX = 80;
+    private readonly meleeMinEnemyDistanceX = 60;
     private readonly meleeOvertakeSpeedGap = 20;
     private readonly allySpacingX = 40;
     private readonly allyOverlapSpacingX = 14;