feat: 新增对话汇总视图，支持跨 session 连续性分析

- 新增 /api/agents/:agentName/conversations API，按 sessionKey 分组汇总
- 新增 /api/agents/:agentName/conversations/:sessionKey/timeline API
- 前端新增「对话汇总」Tab，展示对话级别的统计信息
- 支持展开查看对话下的所有 session 阶段
- 修复 session 文件不存在时返回 404 的问题

功能：
- 显示每个对话的总消息数、Token 数、压缩次数、时长
- 标注原始 session 和压缩后的 session
- 显示对话时间跨度

public/app.js

@@ -1,6 +1,9 @@
 // 状态
 let currentAgent = null;
 let currentSession = null;
+let currentMessage = null;
+let currentView = 'conversations'; // 'conversations' or 'sessions'
+let conversationsData = []; // 缓存对话汇总数据
 
 // API 调用
 async function fetchAPI(endpoint) {
@@ -45,8 +48,9 @@ function formatNumber(num) {
 }
 
 // 截断文本
-function truncate(text, maxLen = 100) {
+function truncate(text, maxLen = 50) {
     if (!text) return '';
+    text = text.replace(/\n/g, ' ').trim();
     if (text.length <= maxLen) return text;
     return text.substring(0, maxLen) + '...';
 }
@@ -79,21 +83,38 @@ async function loadAgents() {
     }
 }
 
+// 切换视图
+function switchView(view) {
+    currentView = view;
+    document.querySelectorAll('.tab-btn').forEach(btn => {
+        btn.classList.toggle('active', btn.dataset.view === view);
+    });
+    document.querySelectorAll('.view-content').forEach(content => {
+        content.classList.remove('active');
+    });
+    document.getElementById(`${view}-view`).classList.add('active');
+}
+
 // 选择智能体
 async function selectAgent(agentName) {
     currentAgent = agentName;
     currentSession = null;
+    currentMessage = null;
     
     // 更新UI
     document.querySelectorAll('.agent-item').forEach(el => el.classList.remove('active'));
     event.target.closest('.agent-item')?.classList.add('active');
     
-    document.getElementById('agent-name-display').textContent = `- ${agentName}`;
+    document.getElementById('agent-name-display').textContent = `🤖 ${agentName}`;
     document.getElementById('session-id-display').textContent = '';
     document.getElementById('messages-list').innerHTML = '<div class="placeholder">请选择一个会话</div>';
+    document.getElementById('message-detail').innerHTML = '<div class="placeholder">请选择一条消息</div>';
     
-    // 加载会话列表
-    await loadSessions(agentName);
+    // 同时加载对话汇总和会话列表
+    await Promise.all([
+        loadConversations(agentName),
+        loadSessions(agentName)
+    ]);
 }
 
 // 加载会话列表
@@ -112,13 +133,15 @@ async function loadSessions(agentName) {
         container.innerHTML = sessions.map(session => `
             <div class="session-item ${currentSession === session.sessionId ? 'active' : ''}" 
                  onclick="selectSession('${agentName}', '${session.sessionId}')">
-                <div class="channel ${session.channel}">${session.channel}</div>
-                <span class="status ${session.status}">${session.status}</span>
+                <div class="session-header">
+                    <span class="channel ${session.channel}">${session.channel}</span>
+                    <span class="status ${session.status}">${session.status}</span>
+                </div>
                 <div class="meta">
                     <span class="model">${session.model}</span>
                     <span>${formatTime(session.updatedAt)}</span>
                 </div>
-                <div class="target">${truncate(session.target, 50)}</div>
+                <div class="target">${truncate(session.target, 40)}</div>
                 <div class="tokens">
                     📊 ${formatNumber(session.totalTokens)} tokens 
                     (${formatNumber(session.inputTokens)} in / ${formatNumber(session.outputTokens)} out)
@@ -130,22 +153,24 @@ async function loadSessions(agentName) {
     }
 }
 
-// 选择会话
+// 选择会话 - 显示消息概览列表
 async function selectSession(agentName, sessionId) {
     currentSession = sessionId;
+    currentMessage = null;
     
     // 更新UI
     document.querySelectorAll('.session-item').forEach(el => el.classList.remove('active'));
     event.target.closest('.session-item')?.classList.add('active');
     
     document.getElementById('session-id-display').textContent = `- ${sessionId.substring(0, 8)}...`;
+    document.getElementById('message-detail').innerHTML = '<div class="placeholder">请选择一条消息查看详情</div>';
     
-    // 加载消息
-    await loadMessages(agentName, sessionId);
+    // 加载消息概览列表
+    await loadMessageSummaries(agentName, sessionId);
 }
 
-// 加载消息
-async function loadMessages(agentName, sessionId) {
+// 加载消息概览列表（不加载完整内容）
+async function loadMessageSummaries(agentName, sessionId) {
     const container = document.getElementById('messages-list');
     container.innerHTML = '<div class="loading">加载中...</div>';
     
@@ -158,13 +183,16 @@ async function loadMessages(agentName, sessionId) {
         }
         
         container.innerHTML = messages.map((msg, index) => `
-            <div class="message-item ${msg.role}" data-agent="${agentName}" data-session="${sessionId}" data-msg-id="${msg.id}">
-                <div class="header">
-                    <span class="role ${msg.role}">${msg.role}</span>
-                    <span class="time">${formatFullTime(msg.timestamp)}</span>
+            <div class="message-summary ${msg.role} ${currentMessage === msg.id ? 'active' : ''}" 
+                 onclick="selectMessage('${agentName}', '${sessionId}', '${msg.id}')">
+                <div class="summary-header">
+                    <span class="role-badge ${msg.role}">${msg.role === 'user' ? '👤' : '🤖'} ${msg.role}</span>
+                    <span class="time">${formatTime(msg.timestamp)}</span>
+                </div>
+                <div class="summary-text">${escapeHtml(msg.summary)}${msg.hasMoreContent ? '...' : ''}</div>
+                <div class="summary-meta">
+                    ${msg.hasMoreContent ? `<span class="more-indicator">📝 ${formatNumber(msg.contentLength)} 字符</span>` : ''}
                 </div>
-                <div class="content ${msg.fullContent ? 'truncated' : ''}">${escapeHtml(msg.content)}</div>
-                ${msg.fullContent ? `<button class="expand-btn" onclick="showFullMessage('${agentName}', '${sessionId}', '${msg.id}')">查看完整内容</button>` : ''}
             </div>
         `).join('');
     } catch (error) {
@@ -172,28 +200,42 @@ async function loadMessages(agentName, sessionId) {
     }
 }
 
-// 显示完整消息
-async function showFullMessage(agentName, sessionId, messageId) {
-    const modal = document.getElementById('message-modal');
-    const content = document.getElementById('modal-content');
+// 选择消息 - 显示完整内容
+async function selectMessage(agentName, sessionId, messageId) {
+    currentMessage = messageId;
     
-    modal.classList.remove('hidden');
-    content.textContent = '加载中...';
+    // 更新UI
+    document.querySelectorAll('.message-summary').forEach(el => el.classList.remove('active'));
+    event.target.closest('.message-summary')?.classList.add('active');
+    
+    // 加载完整消息内容
+    await loadMessageDetail(agentName, sessionId, messageId);
+}
+
+// 加载消息详情（完整内容）
+async function loadMessageDetail(agentName, sessionId, messageId) {
+    const container = document.getElementById('message-detail');
+    container.innerHTML = '<div class="loading">加载中...</div>';
     
     try {
         const msg = await fetchAPI(`/agents/${agentName}/sessions/${sessionId}/messages/${messageId}`);
-        document.getElementById('modal-title').textContent = `${msg.role.toUpperCase()} - ${formatFullTime(msg.timestamp)}`;
-        content.textContent = msg.content;
+        
+        container.innerHTML = `
+            <div class="message-detail-content ${msg.role}">
+                <div class="detail-header">
+                    <span class="role-badge large ${msg.role}">${msg.role === 'user' ? '👤' : '🤖'} ${msg.role}</span>
+                    <span class="time">${formatFullTime(msg.timestamp)}</span>
+                </div>
+                <div class="detail-body">
+                    <pre class="content-text">${escapeHtml(msg.content)}</pre>
+                </div>
+            </div>
+        `;
     } catch (error) {
-        content.textContent = `加载失败: ${error.message}`;
+        container.innerHTML = `<div class="placeholder">加载失败: ${error.message}</div>`;
     }
 }
 
-// 关闭模态框
-function closeModal() {
-    document.getElementById('message-modal').classList.add('hidden');
-}
-
 // HTML 转义
 function escapeHtml(text) {
     const div = document.createElement('div');
@@ -204,16 +246,93 @@ function escapeHtml(text) {
 // 键盘事件
 document.addEventListener('keydown', (e) => {
     if (e.key === 'Escape') {
-        closeModal();
+        // 可以添加关闭操作
     }
 });
 
-// 点击模态框外部关闭
-document.getElementById('message-modal').addEventListener('click', (e) => {
-    if (e.target === e.currentTarget) {
-        closeModal();
+// 加载对话汇总
+async function loadConversations(agentName) {
+    const container = document.getElementById('conversations-list');
+    container.innerHTML = '<div class="loading">加载中...</div>';
+    
+    try {
+        const conversations = await fetchAPI(`/agents/${agentName}/conversations`);
+        conversationsData = conversations;
+        
+        if (conversations.length === 0) {
+            container.innerHTML = '<div class="placeholder">没有找到对话</div>';
+            return;
+        }
+        
+        container.innerHTML = conversations.map((conv, index) => `
+            <div class="conversation-item" onclick="showConversationDetail(${index})">
+                <div class="conv-header">
+                    <span class="conv-title">
+                        💬 对话 ${index + 1}
+                        <span class="conv-badge">${conv.sessionCount} 个会话</span>
+                    </span>
+                </div>
+                <div class="conv-stats">
+                    <span class="stat">📨 消息: <span class="stat-value">${conv.totalMessages}</span></span>
+                    <span class="stat">📊 Token: <span class="stat-value">${formatNumber(conv.totalTokens)}</span></span>
+                    <span class="stat">🔄 压缩: <span class="stat-value">${conv.compactionCount}</span></span>
+                    <span class="stat">⏱️ 时长: <span class="stat-value">${conv.durationHours || '?'}h</span></span>
+                </div>
+                <div class="conv-target">${conv.channel} · ${conv.chatType} · ${truncate(conv.target, 30)}</div>
+                <div class="conv-time">${formatTime(conv.firstStartedAt)} → ${formatTime(conv.lastUpdatedAt)}</div>
+            </div>
+        `).join('');
+    } catch (error) {
+        container.innerHTML = `<div class="placeholder">加载失败: ${error.message}</div>`;
     }
-});
+}
+
+// 显示对话详情（包含该对话下的所有 session）
+function showConversationDetail(index) {
+    const conv = conversationsData[index];
+    if (!conv) return;
+    
+    // 高亮选中的对话
+    document.querySelectorAll('.conversation-item').forEach((el, i) => {
+        el.classList.toggle('active', i === index);
+    });
+    
+    // 切换到会话视图并显示该对话下的 session
+    switchView('sessions');
+    
+    const container = document.getElementById('sessions-list');
+    container.innerHTML = `
+        <div class="conv-sessions-header">
+            <span class="back-btn" onclick="backToConversations()">← 返回</span>
+            💬 ${conv.channel} · ${conv.chatType}
+        </div>
+        ${conv.sessions.map((session, sIndex) => `
+            <div class="session-item" onclick="selectSession('${currentAgent}', '${session.sessionId}')">
+                <div class="session-header">
+                    <span class="channel ${conv.channel}">${conv.channel}</span>
+                    <span class="status ${session.status}">${session.status}</span>
+                    ${sIndex === 0 ? '<span class="conv-badge">原始</span>' : `<span class="conv-badge">压缩 #${sIndex}</span>`}
+                </div>
+                <div class="meta">
+                    <span class="model">${session.model}</span>
+                    <span>${formatTime(session.startedAt)}</span>
+                </div>
+                <div class="tokens">
+                    📊 ${formatNumber(session.totalTokens)} tokens · 📨 ${session.messageCount} 条消息
+                </div>
+                <div class="conv-time">
+                    ${formatTime(session.startedAt)} → ${formatTime(session.updatedAt)}
+                </div>
+            </div>
+        `).join('')}
+    `;
+}
+
+// 返回对话汇总
+function backToConversations() {
+    switchView('conversations');
+    document.querySelectorAll('.conversation-item').forEach(el => el.classList.remove('active'));
+}
 
 // 初始化
 loadAgents();