Tauri's onCloseRequested wrapper already waits for the asynchronous handler and
destroys the window when that handler returns without preventing the event. The
launcher instead prevented every first request, unregistered the active listener
inside its own callback, and relied on an explicit destroy. If that callback did
not complete, the first click only started peer shutdown and a second click
bypassed the removed listener.
Let the first close request follow Tauri's automatic destruction path after
frontend owners and persistence have drained. Keep the listener installed during
that drain, and prevent only repeated requests so they share the first close
without scheduling duplicate destruction. Bootstrap and render failures still
unregister the listener and destroy their empty or failed webview explicitly.
Test Plan:
- `just frontend-test` -- passed (99 tests)
- `just build` -- passed
- `just fmt` -- passed
- `git diff --check` -- passed
- Native GUI close timing was not available in the automated UI surface.
ddidderr
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