Improve post-tutorial guidance for continuous learning

[qingqing-ux]

Problem

• After completing a tutorial, users may choose to browse all courses and then click Continue Editing in the leave-editor dialog, which returns them to the current operation panel.
• At that point, Copilot guidance has ended, Copilot history may be cleared, and the editor does not show a clear completed state or next action.
• Users may not know whether the tutorial is complete, whether they still need to do anything, or how to continue to the next tutorial.

What Needs Improvement

• Keep the post-completion tutorial state visible after users return to the editor.
• Provide a clear continuous-learning entry point in the editor, such as starting the next tutorial.
• Add a post-tutorial Copilot state that can suggest follow-up actions, such as resuming the previous tutorial session or continuing to the next tutorial.
• Avoid clearing key Copilot history when the tutorial completion dialog appears.

Expected Outcome

• After returning to the editor, users can clearly understand that the tutorial is complete and what they can do next.
• The tutorial flow continues naturally after completion instead of leaving users in an intermediate state.

Acceptance Criteria

• Users can still see the completed tutorial state after returning to the editor.
• The editor provides a next-step entry point for continued learning.
• Copilot preserves necessary context or provides follow-up guidance after tutorial completion.
• The tutorial completion dialog does not clear key Copilot history.

[Ethanlita]

Actually, there are some messages in the Copilot window before the tutorial-finish pop-up. However, once the pop-up window appeared, all copilot messages disappeared. Maybe we have to disable the copilot history clearing function.

[qingqing-ux]

补充说明：

• 持续学习入口放到 #3295 考虑。
• 用户需要看到学习位置，并继续下一节。
• 它属于列表 / 课程地图侧，不属于 #3292 的编辑器闭环。