feat:实现任务历史加载功能 - 完整还原对话样式

主要改进：
1. 实现selectConversation功能，支持点击任务历史列表加载会话
2. 优化会话存储格式，保存完整的segments信息（包括工具调用）
3. 添加旧格式到新格式的自动转换，兼容历史数据
4. 改进错误处理，自动清理无效的空任务目录
5. 优化路径编码逻辑，确保跨平台一致性
6. 前端支持clearChat、addUserMessage、addAiMessage命令

技术细节：
- 扩展AiMessage数据结构，添加segments字段
- 修改messageHandler保存逻辑，将完整segments保存到一条消息
- 实现loadTaskSession方法，加载指定任务的完整会话
- 添加自动清理机制，删除无效的空任务目录

src/views/conversationHistoryBar.ts

@@ -111,6 +111,10 @@ export function getConversationHistoryBarStyles(): string {
       cursor: pointer;
       transition: background 0.2s ease;
       border-bottom: 1px solid var(--vscode-panel-border);
+      display: flex;
+      align-items: center;
+      justify-content: space-between;
+      gap: 12px;
     }
 
     .history-item:last-child {
@@ -124,15 +128,17 @@ export function getConversationHistoryBarStyles(): string {
     .history-item-title {
       font-size: 14px;
       font-weight: 500;
-      margin-bottom: 4px;
       white-space: nowrap;
       overflow: hidden;
       text-overflow: ellipsis;
+      flex: 1;
     }
 
     .history-item-time {
       font-size: 12px;
       opacity: 0.7;
+      white-space: nowrap;
+      flex-shrink: 0;
     }
 
     .history-empty {
@@ -142,6 +148,14 @@ export function getConversationHistoryBarStyles(): string {
       font-size: 14px;
     }
 
+    .history-load-more {
+      padding: 12px 16px;
+      text-align: center;
+      color: var(--vscode-descriptionForeground);
+      font-size: 12px;
+      border-top: 1px solid var(--vscode-panel-border);
+    }
+
     .new-conversation-button {
       width: 36px;
       height: 36px;
@@ -199,6 +213,12 @@ export function getConversationHistoryBarScript(): string {
     // 会话历史相关变量
     let conversationHistory = [];
     let currentConversationId = null;
+    let currentOffset = 0;
+    let totalHistory = 0;
+    let hasMoreHistory = false;
+    let isLoadingHistory = false;
+    const HISTORY_PAGE_SIZE = 10;
+    const MAX_HISTORY_ITEMS = 100;
 
     // 切换历史记录下拉菜单
     function toggleHistoryDropdown() {
@@ -211,33 +231,90 @@ export function getConversationHistoryBarScript(): string {
       } else {
         menu.classList.add('active');
         button.classList.add('active');
-        // 加载会话历史
-        loadConversationHistory();
+        // 重置并加载会话历史
+        resetAndLoadHistory();
       }
     }
 
-    // 加载会话历史
-    function loadConversationHistory() {
-      vscode.postMessage({ command: 'loadConversationHistory' });
+    // 重置并加载会话历史
+    function resetAndLoadHistory() {
+      conversationHistory = [];
+      currentOffset = 0;
+      totalHistory = 0;
+      hasMoreHistory = false;
+      const historyList = document.getElementById('historyList');
+      if (historyList) {
+        historyList.innerHTML = '<div class="history-empty">加载中...</div>';
+      }
+      loadMoreHistory();
     }
 
-    // 渲染会话历史列表
-    function renderConversationHistory(history) {
-      conversationHistory = history;
-      const historyList = document.getElementById('historyList');
+    // 加载更多会话历史
+    function loadMoreHistory() {
+      if (isLoadingHistory || (currentOffset > 0 && !hasMoreHistory)) {
+        return;
+      }
 
-      if (!history || history.length === 0) {
+      // 检查是否已达到最大数量
+      if (currentOffset >= MAX_HISTORY_ITEMS) {
+        return;
+      }
+
+      isLoadingHistory = true;
+      vscode.postMessage({
+        command: 'loadConversationHistory',
+        offset: currentOffset,
+        limit: HISTORY_PAGE_SIZE
+      });
+    }
+
+    // 渲染会话历史列表（支持追加）
+    function renderConversationHistory(data) {
+      isLoadingHistory = false;
+
+      if (!data || !data.items) {
+        return;
+      }
+
+      // 追加新数据
+      conversationHistory = conversationHistory.concat(data.items);
+      totalHistory = data.total;
+      hasMoreHistory = data.hasMore;
+      currentOffset += data.items.length;
+
+      const historyList = document.getElementById('historyList');
+      if (!historyList) {
+        return;
+      }
+
+      // 如果没有任何历史记录
+      if (conversationHistory.length === 0) {
         historyList.innerHTML = '<div class="history-empty">暂无会话历史</div>';
         return;
       }
 
-      historyList.innerHTML = history.map(item => \`
-        <div class="history-item"
-             onclick="selectConversation('\${item.id}')">
+      // 渲染所有历史记录
+      historyList.innerHTML = conversationHistory.map(item => \`
+        <div class="history-item" onclick="selectConversation('\${item.id}')">
           <div class="history-item-title">\${item.title || '未命名会话'}</div>
           <div class="history-item-time">\${formatTime(item.timestamp)}</div>
         </div>
       \`).join('');
+
+      // 如果还有更多数据，添加"加载更多"提示
+      if (hasMoreHistory && currentOffset < MAX_HISTORY_ITEMS) {
+        historyList.innerHTML += \`
+          <div class="history-load-more" id="loadMoreIndicator">
+            <span>滚动加载更多...</span>
+          </div>
+        \`;
+      } else if (currentOffset >= MAX_HISTORY_ITEMS && hasMoreHistory) {
+        historyList.innerHTML += \`
+          <div class="history-load-more">
+            <span>已显示最近 \${MAX_HISTORY_ITEMS} 条记录</span>
+          </div>
+        \`;
+      }
     }
 
     // 选择会话
@@ -291,6 +368,22 @@ export function getConversationHistoryBarScript(): string {
       });
     }
 
+    // 监听下拉菜单滚动事件
+    const historyDropdownMenu = document.getElementById('historyDropdownMenu');
+    if (historyDropdownMenu) {
+      historyDropdownMenu.addEventListener('scroll', () => {
+        const menu = historyDropdownMenu;
+        const scrollTop = menu.scrollTop;
+        const scrollHeight = menu.scrollHeight;
+        const clientHeight = menu.clientHeight;
+
+        // 当滚动到距离底部 50px 时，加载更多
+        if (scrollHeight - scrollTop - clientHeight < 50) {
+          loadMoreHistory();
+        }
+      });
+    }
+
     // 点击外部关闭下拉菜单
     document.addEventListener('click', (event) => {
       const container = document.querySelector('.history-dropdown-container');