When autosave is off, unsaved work prompt is not respected by commands that close the window automatically

[audionerd]

Steps

• In Preferences, set "Save Project Data Automatically" to false
• Draw on a board
• Try one of the following commands:
  • "Clean Up Scene"
  • "Open File"
  • Dropping a .storyboarder file onto the window
  • ... maybe other commands? TBD

For example, with "Clean Up Scene"

• See "Clean Up deletes unused image files … Are you sure?" dialog
• Press "Yes"
• See "Your Storyboarder file is not saved. Are you sure you want to close the workspace?" dialog
• Press "No"
• Cleanup still runs and any unsaved work is lost

What should happen:
If you cancel the "Are you sure you want to close the workspace?", the other dependent operation should be prevented as well.

Related to #751

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Maybe commands that automatically close the window should wait for affirmative prompt response (e.g. check if readyToClose is true)?