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/skill/TooltipCom.ts

@@ -146,10 +146,10 @@ export class TooltipCom extends CCComp {
                 this.node.setPosition(v3(this.node.position.x, currentY - 60));
                 this.node.setSiblingIndex(topSiblingIndex);
                 break;
-            case TooltipTypes.shield: // 护盾格挡
+            case TooltipTypes.shield: // 护盾减免
                 this.node.setPosition(v3(this.node.position.x + offsetX, currentY));
                 this.node.setSiblingIndex(topSiblingIndex);
-                this.setupLabel("add_life", "hp", "格挡");
+                this.setupLabel("add_life", "hp", "减免");
                 isHeal = true;
                 break;
         }