When quitting or closing the graphcode, Show a pop up to stop the sessions or continue the sessions.

[scgopi]

Describe the bug
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To reproduce
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2. Click on '...'
3. See error

Expected behavior
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Screenshots
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Environment

• GraphCode version: [e.g., 0.1.28-beta1]
• macOS version: [e.g., 15.0]
• Backend: [e.g., Claude Code, Copilot CLI]

Additional context
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