Destroy the taskbar icon when a window crashes

[dominicletz]

Summary

• A crashed Desktop.Window used to leave the native tray icon in place.
• Desktop.Menu now traps the parent exit, stops, and calls set_icon(nil) so the adapter can destroy the icon.
• Window crash cleanup also stops the taskbar menu if it is still alive.

Test plan

• NO_WX=1 mix test.fast test/desktop/menu_crash_test.exs
• Restart an app after a window crash and confirm one tray icon.

Made with Cursor

[cursor]

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