feat(英雄/怪物): 添加受击倒地特效

- 新增 down.prefab 和 down.anim 资源文件
- 在 Hero 和 Monster 的落地逻辑中调用 playEnd("down") 播放特效
- 优化 HeroViewComp 中特效生成逻辑，移除冗余的组件销毁操作

assets/script/game/hero/Hero.ts

@@ -105,6 +105,7 @@ export class Hero extends ecs.Entity {
             .call(() => {
                 if (!node || !node.isValid) return;
                 node.setPosition(pos.x, dropToY, 0);
+                hv.playEnd("down");
                 move.moving = true;
                 if (collider) {
                     collider.enabled = true;

assets/script/game/hero/HeroViewComp.ts

@@ -334,8 +334,6 @@ export class HeroViewComp extends CCComp {
     private spawnTimedFx(path: string, parent: Node | null, life: number = 0.8, worldPos?: Vec3): Node | null {
         const node = this.createFxNode(path, parent, worldPos);
         if (!node) return null;
-        const ender = node.getComponent(oneCom);
-        if (ender) ender.destroy();
         const timer = node.getComponent(timedCom) || node.addComponent(timedCom);
         timer.time = Math.max(0.2, life);
         return node;
@@ -343,8 +341,6 @@ export class HeroViewComp extends CCComp {
     private spawnAnimEndFx(path: string, parent: Node | null, worldPos?: Vec3): Node | null {
         const node = this.createFxNode(path, parent, worldPos);
         if (!node) return null;
-        const timer = node.getComponent(timedCom);
-        if (timer) timer.destroy();
         node.getComponent(oneCom) || node.addComponent(oneCom);
         return node;
     }

assets/script/game/hero/Mon.ts

@@ -171,6 +171,7 @@ export class Monster extends ecs.Entity {
             .call(() => {
                 if (!node || !node.isValid) return;
                 node.setPosition(pos.x, dropToY, 0);
+                view.playEnd("down");
                 move.moving = true;
                 if (collider) {
                     collider.enabled = true;