(bjogui dialogs) has alert, confirm and prompt, the open, save and folder
pickers, and quit, each a command whose answer comes back as a message. A
dialog is a window, which only the UI thread may make, so the command posts
it there and awaits its Task in a fiber. Avalonia's dialogs take no
CancellationToken, so they cannot be task->event; the Task is awaited
through the non-generic Task.WhenAll, and its result read by reflection,
because Bjolang reads no Task's Result.
With no window, as under start-app, each answers as if cancelled.
run-app's #:on-close turns the close button into a message, and quit
closes the windows by program, which is not asked again.
🤖 Generated with [ECA](https://eca.dev) (anthropic/claude-opus-4-8)
Co-Authored-By: eca-agent <git@eca.dev>
