some fixes

python_app/gui/main.py

@@ -40,10 +40,17 @@ def _install_unix_signal_handlers(app: QApplication, window: AppWindow) -> None:
     loop just long enough to deliver pending signals.
     """
 
-    def _request_shutdown(*_args: object) -> None:
+    def _shutdown() -> None:
         window.close()
         app.quit()
 
+    def _request_shutdown(signum: int, _frame: object) -> None:
+        # Async-signal-safe: do the minimum from C signal context. Reset the handler
+        # to default so a second signal force-terminates instead of re-entering Qt
+        # teardown, then schedule the real shutdown on the next event-loop iteration.
+        signal.signal(signum, signal.SIG_DFL)
+        QTimer.singleShot(0, _shutdown)
+
     for sig in (signal.SIGINT, signal.SIGTERM):
         signal.signal(sig, _request_shutdown)