fix(merch detail): fix header style and optimize list toggle

1. 修正商品详情页头部容器的样式选择器和优先级问题
2. 调整商品数据监听，改为监听商品描述而非整个merch对象
3. 给列表切换逻辑添加防抖处理，避免频繁切换触发过多渲染
4. 新增列表切换的防抖工具函数

pages_promotion/merch/detail.vue

@@ -322,20 +322,20 @@ export default {
 		return {
 			headerHeight: 320,
 			screenWidth: uni.getSystemInfoSync().windowWidth,
-			headerHeightInited: false
+			headerHeightInited: false,
+			changeStyleDebounce: null
 		};
 	},
 	mixins: [list],
 	watch: {
-		merch: {
+		'merch.desc': {
 			handler() {
 				if (!this.headerHeightInited) {
 					this.$nextTick(() => {
 						this.initHeaderHeight();
 					});
 				}
-			},
-			deep: true
+			}
 		}
 	},
 	methods: {
@@ -358,6 +358,13 @@ export default {
 					}
 				}).exec();
 			}, 100);
+		},
+		changeListStyle() {
+			if (this.changeStyleDebounce) clearTimeout(this.changeStyleDebounce);
+			this.changeStyleDebounce = setTimeout(() => {
+				this.isList = !this.isList;
+				this.waterfallflow(0);
+			}, 50);
 		}
 	},
 	mounted() {
@@ -370,8 +377,8 @@ export default {
 @import './public/css/list.scss';
 </style>
 <style scoped>
-.head-wrap {
-	top: 0;
+view.head-wrap {
+	top: -1 !important;
 }
 
 .merch-image-wrap {