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/HeroViewComp.ts

@@ -349,7 +349,7 @@ export class HeroViewComp extends CCComp {
         Tooltip.load(pos, type, value, s_uuid, this.node.parent, 1, this.model?.fac ?? FacSet.MON);
     }
 
-    /** 护盾格挡提示 */
+    /** 护盾减免提示 */
     shield_tip(absorbed: number) {
         this.hp_tip(TooltipTypes.shield, NumberFormatter.formatNumber(Math.max(0, Math.floor(absorbed))));
     }