refactor: 重构护盾机制为数值减免型

1. 调整护盾逻辑：从单次抵挡改为按伤害量减免
2. 更新配置、注释与UI提示文本，统一术语表述
3. 修复prefab布局适配新的护盾显示样式

assets/script/game/hero/HeroAttrsComp.ts

@@ -153,11 +153,11 @@ export class HeroAttrsComp extends ecs.Comp {
         const addValue = Math.max(0, Math.floor(value));
         if (addValue <= 0) return;
         this.shield += addValue;
-        this.shield = Math.min(this.shield, FightSet.SHIELD_MAX); // 限制护盾最大层数
+        this.shield = Math.min(this.shield, FightSet.SHIELD_MAX); // 限制护盾值上限（数值减免型）
         if (this.shield < 0) this.shield = 0;
         this.dirty_shield = true;  // 标记护盾需要更新
         if (this.debugMode) {
-            mLogger.log(this.debugMode, 'HeroAttrs', ` 护盾次数变更: ${this.hero_name}, 变化=${addValue}, ${Math.floor(oldShield)} -> ${Math.floor(this.shield)}`);
+            mLogger.log(this.debugMode, 'HeroAttrs', ` 护盾值变更: ${this.hero_name}, 变化=${addValue}, ${Math.floor(oldShield)} -> ${Math.floor(this.shield)}`);
         }
     }
     add_hp_max(value: number) {