(task from #1983)

If you change focus out of (tab away from) VS Code, the prompt stays visible.

This is controlled by the QuickPick.ignoreFocusOut property. We only use window.showQuickPick(), so the property is set via the ignoreFocusOut option. All related quick picks need to have that property set to true. This may be manageable via ApplicationShell.showQuickPick() (in src/client/common/application/applicationShell.ts).