feat: add history report switcher dropdown in report detail view

webapp/static/css/app.css

@@ -316,6 +316,24 @@ table.group-table td { border-bottom: 1px solid #f1f5f9; font-variant-numeric: t
   font-size: 13px; display: flex; align-items: center; gap: 6px;
 }
 
+/* ---------- 报告历史切换下拉 ---------- */
+.report-switcher {
+  display: flex; align-items: center; gap: 10px;
+  background: var(--surface); border: 1px solid var(--line);
+  border-radius: var(--radius); padding: 10px 16px;
+  margin-bottom: 14px; box-shadow: var(--shadow);
+}
+.report-switcher-label {
+  font-size: 13px; font-weight: 600; color: var(--slate); white-space: nowrap;
+}
+.report-switcher-select {
+  flex: 1; min-width: 0;
+  border: 1px solid var(--line); border-radius: 6px; padding: 6px 10px;
+  font-size: 13px; font-family: inherit; background: var(--bg); color: var(--ink);
+  cursor: pointer;
+}
+.report-switcher-select:focus { outline: none; border-color: var(--petrol); }
+
 /* ================================================================
    打印样式（导出 PDF 用）
    浏览器打印时隐藏 UI chrome，保留报告内容，图表 canvas 原样输出

webapp/static/index.html

@@ -103,6 +103,14 @@
 
       <!-- 报告详情视图 -->
       <section class="view" id="view-report" hidden>
+        <!-- 历史报告切换下拉（顶部，始终可见） -->
+        <div class="report-switcher no-print" id="report-switcher">
+          <label class="report-switcher-label">切换报告</label>
+          <select class="select report-switcher-select" id="report-switcher-select">
+            <option value="">— 加载中… —</option>
+          </select>
+        </div>
+
         <div class="empty" id="report-empty">
           <p>请先从「运行列表」选择一次运行。</p>
         </div>

webapp/static/js/report.js

@@ -4,11 +4,16 @@ const Report = {
   distChart: null,
   currentDetail: null,
   activeGrouping: null,
+  _switcherLoaded: false,
 
   // 加载并渲染指定运行的完整报告。
   async render(runId) {
     const empty = document.getElementById("report-empty");
     const content = document.getElementById("report-content");
+
+    // 加载历史报告下拉（仅首次）
+    Report._loadSwitcher(runId);
+
     if (!runId) {
       empty.hidden = false;
       content.hidden = true;
@@ -28,6 +33,10 @@ const Report = {
       Report.renderLowest(detail.report);
       Report.renderAdvice(detail.summary, detail.report);
       content.style.opacity = "1";
+
+      // 同步下拉选中项
+      const sel = document.getElementById("report-switcher-select");
+      if (sel) sel.value = runId;
     } catch (err) {
       empty.hidden = false;
       content.hidden = true;
@@ -35,6 +44,55 @@ const Report = {
     }
   },
 
+  // 加载并填充历史报告下拉选择框
+  async _loadSwitcher(currentRunId) {
+    const sel = document.getElementById("report-switcher-select");
+    if (!sel) return;
+
+    // 已加载过就只更新选中值，不重复请求
+    if (Report._switcherLoaded) {
+      if (currentRunId) sel.value = currentRunId;
+      return;
+    }
+
+    try {
+      const data = await API.runs();
+      const runs = data.runs || [];
+      sel.innerHTML = "";
+      if (runs.length === 0) {
+        sel.innerHTML = '<option value="">（无历史运行）</option>';
+        return;
+      }
+      runs.forEach((run) => {
+        const opt = document.createElement("option");
+        opt.value = run.run_id;
+        const timeStr = App.shortTime(run.finished_at);
+        const meanText = run.metric_means
+          ? Object.entries(run.metric_means)
+              .filter(([, v]) => v !== null && v !== undefined)
+              .slice(0, 2)
+              .map(([k, v]) => `${App.shortMetric(k)}=${v.toFixed(2)}`)
+              .join(" ")
+          : "";
+        opt.textContent = `${run.scenario_name || run.run_id}  ${timeStr}${meanText ? "  [" + meanText + "]" : ""}`;
+        sel.appendChild(opt);
+      });
+      Report._switcherLoaded = true;
+      if (currentRunId) sel.value = currentRunId;
+    } catch (_e) {
+      sel.innerHTML = '<option value="">（加载失败）</option>';
+    }
+
+    // 绑定切换事件（只绑一次）
+    sel.addEventListener("change", () => {
+      const rid = sel.value;
+      if (!rid) return;
+      App.currentRunId = rid;
+      App.enableReportNav();
+      Report.render(rid);
+    });
+  },
+
   // 顶部元信息条。
   renderMeta(summary) {
     const el = document.getElementById("report-meta");