Guard the news detail panel against stale responses and load errors

The detail is now a persistent side panel, so quick clicks can interleave
requests: only the latest request's result is applied, and a failed load
shows an error state with a retry button instead of spinning forever.

Also correct the position history comments: only plans from before plan
3.1 could hand their position over to a replacing plan.

backend/src/alphapulse/api/trading.py

@@ -149,7 +149,7 @@ class PositionHistoryOut(BaseModel):
     opened_at: datetime
     closed_at: datetime
     close_reason: str
-    # 本计划的入场成交；计划被替换时持仓由新计划接管，新计划没有自己的入场成交，这两项为空
+    # 本计划的入场成交。计划 3.1 之前，替换计划时持仓会交给新计划接管（如 #8），这类旧记录没有自己的入场成交，这两项为空
     quantity: Decimal | None
     entry_price: Decimal | None
     # 止盈、止损、市价平仓的成交均价；外部平仓（如网页手动平仓）没有成交记录，为空

web/src/apis/trading.ts

@@ -275,7 +275,7 @@ export interface PositionHistory {
   opened_at: string
   closed_at: string
   close_reason: string
-  /** 计划被替换后接管持仓的新计划没有自己的入场成交，为空 */
+  /** 计划 3.1 之前替换计划时会接管旧计划的持仓，这类旧记录没有自己的入场成交，为空 */
   quantity: string | null
   entry_price: string | null
   /** 外部平仓没有成交记录，为空 */

web/src/pages/news/components/NewsDetail.vue

@@ -13,16 +13,36 @@ const revisions = ref<Revision[]>([])
 const activeTab = ref("content")
 // 当前查看的修订序号，与上一版对比
 const selectedRevision = ref<number>()
+// 加载失败（错误提示已由 http 拦截器弹出）：停止转圈，显示重试
+const failed = ref(false)
+// 连续点击不同新闻时，只采用最后一次请求的结果
+let requestSeq = 0
 
-watch(() => props.newsId, async (id) => {
-  if (id == null)
-    return
-  activeTab.value = "content"
-  detail.value = undefined
+async function load(id: number) {
+  const seq = ++requestSeq
+  failed.value = false
+  try {
     const [news, revs] = await Promise.all([getNews(id), listRevisions(id)])
+    if (seq !== requestSeq)
+      return
     detail.value = news
     revisions.value = revs
     selectedRevision.value = revs[0]?.revision_no
+  } catch (error) {
+    if (seq === requestSeq)
+      failed.value = true
+    throw error
+  }
+}
+
+watch(() => props.newsId, (id) => {
+  activeTab.value = "content"
+  detail.value = undefined
+  revisions.value = []
+  if (id == null)
+    requestSeq++
+  else
+    load(id)
 })
 
 // 第三方正文放进无脚本权限的 sandbox iframe，避免其中的脚本访问本站
@@ -110,6 +130,11 @@ const diffStats = computed(() => ({
         </el-tab-pane>
       </el-tabs>
     </template>
+    <el-empty v-else-if="failed" description="加载失败" class="m-auto">
+      <el-button type="primary" @click="load(newsId)">
+        重试
+      </el-button>
+    </el-empty>
     <div v-else v-loading="true" class="h-full" />
   </el-card>
 </template>