Allow to pause work on a session

When I go home I need to close the application and would want a pause button so I don't wait 20 minutes for a session to complete and then have to close it anyway and loose the work that was done in those 20 minutes.

该 issue 未指出任何文件、测试或入口点。首先明确会话暂停和恢复的行为，包括应用程序关闭时如何保留工作，然后确定相关的会话生命周期代码和测试。完成标准是：会话可以在关闭前暂停，并在恢复时不会丢失已完成的工作。

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