fix(interview): repair interview-history endpoint and surface past interviews in UI

The interview-history feature already existed (interviews are recorded to each
platform's OASIS sqlite DB and `POST /api/simulation/interview/history` reads
them) but was broken on two fronts:

1. Backend crash: get_interview_history sorts merged twitter+reddit results by
   "timestamp", but the two platforms store created_at with different types
   (one int-like, one datetime string), raising
   "'<' not supported between instances of 'int' and 'str'". Coerce the sort
   key to str so mixed-type timestamps sort safely.

2. Step 5 (Interaction) never loaded that history, so past interviews vanished
   on reload. Add getInterviewHistory() and load it on mount, seeding the
   per-agent chat cache (chronological, prompt-prefix stripped, deduped across
   platforms) so selecting an agent shows prior Q&A.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/app/services/simulation_runner.py

@@ -1757,8 +1757,8 @@ class SimulationRunner:
             )
             results.extend(platform_results)
         
-        # 按时间降序排序
+        # 按时间降序排序（不同平台 created_at 可能是 int 或 datetime 字符串，统一转字符串避免类型比较报错）
-        results.sort(key=lambda x: x.get("timestamp", ""), reverse=True)
+        results.sort(key=lambda x: str(x.get("timestamp", "")), reverse=True)
         
         # 如果查询了多个平台，限制总数
         if len(platforms) > 1 and len(results) > limit:

frontend/src/api/simulation.js

@@ -176,6 +176,18 @@ export const interviewAgents = (data) => {
   return requestWithRetry(() => service.post('/api/simulation/interview/batch', data), 3, 1000)
 }
 
+/**
+ * 获取某个模拟的采访历史（持久化记录，从 OASIS 数据库读取）
+ * @param {string} simulationId
+ * @param {Object} opts - { platform?, agent_id?, limit? }
+ */
+export const getInterviewHistory = (simulationId, opts = {}) => {
+  return service.post('/api/simulation/interview/history', {
+    simulation_id: simulationId,
+    ...opts
+  })
+}
+
 /**
  * 获取历史模拟列表（带项目详情）
  * 用于首页历史项目展示

frontend/src/components/Step5Interaction.vue

@@ -414,7 +414,7 @@
 import { ref, computed, watch, onMounted, onUnmounted, nextTick } from 'vue'
 import { useI18n } from 'vue-i18n'
 import { chatWithReport, getReport, getAgentLog } from '../api/report'
-import { interviewAgents, getSimulationProfilesRealtime } from '../api/simulation'
+import { interviewAgents, getSimulationProfilesRealtime, getInterviewHistory } from '../api/simulation'
 
 const { t } = useI18n()
 
@@ -928,6 +928,60 @@ const loadProfiles = async () => {
   }
 }
 
+// 去掉 optimize_interview_prompt 注入的前缀，仅展示用户真实问题
+const stripInterviewPrefix = (p) => {
+  if (!p) return ''
+  for (const marker of ['我的问题是：', '我的问题是:', '问题：', '问题:']) {
+    const idx = p.indexOf(marker)
+    if (idx >= 0) return p.slice(idx + marker.length).trim()
+  }
+  return p
+}
+
+// 加载已持久化的采访历史（来自 OASIS 数据库），按 agent 填充对话缓存（刷新后仍可见）
+const loadInterviewHistory = async () => {
+  if (!props.simulationId) return
+  try {
+    const res = await getInterviewHistory(props.simulationId, { limit: 200 })
+    // 后端返回 { history: [{ agent_id, prompt, response, platform, timestamp }] }（按时间降序）
+    const records = res.success && res.data ? (res.data.history || []) : []
+    if (!records.length) return
+
+    // 按 agent_id 分组，时间升序，按(问题+回答)去重（同一问题可能跨双平台各记一条）
+    const byAgent = {}
+    records
+      .slice()
+      .sort((a, b) => String(a.timestamp).localeCompare(String(b.timestamp)))
+      .forEach(rec => {
+        const aid = rec.agent_id
+        if (!(aid in byAgent)) byAgent[aid] = { seen: new Set(), msgs: [] }
+        const prompt = stripInterviewPrefix(rec.prompt || '')
+        const answer = typeof rec.response === 'string' ? rec.response : JSON.stringify(rec.response)
+        const dedupeKey = prompt + '|' + answer
+        if (byAgent[aid].seen.has(dedupeKey)) return
+        byAgent[aid].seen.add(dedupeKey)
+        byAgent[aid].msgs.push(
+          { role: 'user', content: prompt, timestamp: rec.timestamp },
+          { role: 'assistant', content: answer, timestamp: rec.timestamp }
+        )
+      })
+
+    // 历史在前，本会话新对话在后
+    Object.keys(byAgent).forEach(aid => {
+      const key = `agent_${aid}`
+      chatHistoryCache.value[key] = [...byAgent[aid].msgs, ...(chatHistoryCache.value[key] || [])]
+    })
+
+    // 若已选中某个 Agent，立即刷新其对话视图
+    if (chatTarget.value !== 'report_agent' && selectedAgentIndex.value != null) {
+      chatHistory.value = chatHistoryCache.value[`agent_${selectedAgentIndex.value}`] || []
+    }
+    addLog(`Loaded ${records.length} interview record(s) from history`)
+  } catch (err) {
+    console.warn('加载采访历史失败:', err)
+  }
+}
+
 // Click outside to close dropdown
 const handleClickOutside = (e) => {
   const dropdown = document.querySelector('.agent-dropdown')
@@ -941,6 +995,7 @@ onMounted(() => {
   addLog(t('log.step5Init'))
   loadReportData()
   loadProfiles()
+  loadInterviewHistory()
   document.addEventListener('click', handleClickOutside)
 })