refactor(merch/detail): 优化商品详情页头部高度初始化逻辑

1. 移除冗余的headerHeightInited状态和监听逻辑
2. 提取获取商品详情的逻辑为单独getMerch方法
3. 移除initHeaderHeight的延迟定时器并修复top样式值

pages_promotion/merch/detail.vue

@@ -322,23 +322,27 @@ export default {
 		return {
 			headerHeight: 320,
 			screenWidth: uni.getSystemInfoSync().windowWidth,
-			headerHeightInited: false,
 			changeStyleDebounce: null
 		};
 	},
 	mixins: [list],
-	watch: {
-		'merch.desc': {
-			handler() {
-				if (!this.headerHeightInited) {
+	methods: {
+		getMerch() {
+			this.$api.sendRequest({
+				url: '/merch/api/merch/merchinfo',
+				data: {
+					merch_id: this.merch_id
+				},
+				success: res => {
+					if (res.code >= 0 && res.data) {
+						this.merch = res.data;
 						this.$nextTick(() => {
 							this.initHeaderHeight();
 						});
 					}
 				}
-		}
+			});
 		},
-	methods: {
 		showFullDesc() {
 			if (this.merch.desc) {
 				uni.showModal({
@@ -349,15 +353,12 @@ export default {
 			}
 		},
 		initHeaderHeight() {
-			setTimeout(() => {
 			const query = uni.createSelectorQuery().in(this);
 			query.select('.head-wrap').boundingClientRect(rect => {
 				if (rect && rect.height > 0) {
 					this.headerHeight = (rect.height / this.screenWidth) * 750;
-						this.headerHeightInited = true;
 				}
 			}).exec();
-			}, 100);
 		},
 		changeListStyle() {
 			if (this.changeStyleDebounce) clearTimeout(this.changeStyleDebounce);
@@ -377,8 +378,8 @@ export default {
 @import './public/css/list.scss';
 </style>
 <style scoped>
-view.head-wrap {
-	top: -1 !important;
+.head-wrap {
+	top: 0;
 }
 
 .merch-image-wrap {