refactor(hero): 移除 Boss 阶段描边相关未实现的代码

清理了 Boss 阶段描边功能的相关代码，包括移除了 resetPhaseOutline 和 setPhaseOutline 方法，删除了相关材质定义，将 onPhaseEnter 方法置空待后续迭代实现。

assets/script/game/hero/hit-flash-white/scripts/FlashSprite.ts

@@ -19,9 +19,6 @@ export class FlashSprite extends Component {
     @property({ type: Material, tooltip: '黄色描边材质(5级)' })
     outlineMatYellow: Material | null = null;
 
-    @property({ type: Material, tooltip: '红色描边材质(Boss阶段3)' })
-    outlineMatRed: Material | null = null;
-
     orginalFlashMaterial: Material | null = null;
     defaultMaterial: Material | null = null; // 缓存最原始的无描边材质
     sprite: Sprite | null = null;
@@ -67,31 +64,6 @@ export class FlashSprite extends Component {
         }
     }
 
-    /**
-     * 设置 Boss 阶段描边（与等级描边互斥，阶段优先）
-     * @param phase 阶段索引 0=P1(无描边/恢复默认) 1=P2(绿) 2=P3(红)
-     */
-    public setPhaseOutline(phase: number) {
-        if (!this.sprite) {
-            this.sprite = this.node.getComponent(Sprite);
-        }
-
-        let targetMat: Material | null = null;
-        if (phase === 1) {
-            targetMat = this.outlineMatGreen;
-        } else if (phase >= 2) {
-            targetMat = this.outlineMatRed;
-        } else {
-            // P1 / 复位：恢复最原始的无描边材质
-            targetMat = this.defaultMaterial;
-        }
-
-        if (targetMat && this.sprite) {
-            this.orginalFlashMaterial = targetMat;
-            this.sprite.setSharedMaterial(targetMat, 0);
-        }
-    }
-
     public clickFlash() {
         if (!this.sprite || !this.hitFlashMaterial) return;