feat(session): 实现会话保存和加载功能

- 在 AcpConnection 和 AcpSessionManager 中添加会话保存方法
- 在 QwenAgentManager 中实现通过 ACP 和直接保存会话的功能
- 在前端添加保存会话对话框和相关交互逻辑
- 新增 QwenSessionManager 用于直接操作文件系统保存和加载会话

packages/vscode-ide-companion/src/webview/ClaudeCodeStyles.css

@@ -7,6 +7,19 @@
  * Path: /Users/jinjing/Downloads/Anthropic.claude-code-2.0.43/extension/webview/index.css
  */
 
+/* Import component styles */
+@import './components/SaveSessionDialog.css';
+@import './components/SessionManager.css';
+@import './components/MessageContent.css';
+@import './components/EmptyState.css';
+@import './components/CompletionMenu.css';
+@import './components/ContextPills.css';
+@import './components/PermissionDrawer.css';
+@import './components/PlanDisplay.css';
+@import './components/Timeline.css';
+@import './components/shared/FileLink.css';
+@import './components/toolcalls/shared/DiffDisplay.css';
+
 /* ===========================
    Header Styles (from Claude Code .he)
    =========================== */