fix(updater,ci): headless tests and immediate app shutdown

- stub PySide6 in test_updater_gui to run on linux runner without libGL

- close main app immediately after launching updater, without blocking OK dialog

tests/test_updater_gui.py

@@ -1,10 +1,76 @@
 import importlib.util
+import sys
 import tempfile
 import unittest
 from pathlib import Path
+import types
+
+
+def _install_pyside6_stubs():
+    if "PySide6" in sys.modules:
+        return
+
+    pyside6_module = types.ModuleType("PySide6")
+    qtcore_module = types.ModuleType("PySide6.QtCore")
+    qtgui_module = types.ModuleType("PySide6.QtGui")
+    qtwidgets_module = types.ModuleType("PySide6.QtWidgets")
+
+    class _Signal:
+        def __init__(self, *args, **kwargs):
+            pass
+
+        def connect(self, *args, **kwargs):
+            pass
+
+    class _QObject:
+        pass
+
+    class _QThread:
+        def __init__(self, *args, **kwargs):
+            pass
+
+    class _QTimer:
+        @staticmethod
+        def singleShot(*args, **kwargs):
+            pass
+
+    class _QUrl:
+        @staticmethod
+        def fromLocalFile(path):
+            return path
+
+    class _QDesktopServices:
+        @staticmethod
+        def openUrl(*args, **kwargs):
+            return True
+
+    class _Widget:
+        def __init__(self, *args, **kwargs):
+            pass
+
+    qtcore_module.QObject = _QObject
+    qtcore_module.Qt = type("Qt", (), {})
+    qtcore_module.QThread = _QThread
+    qtcore_module.Signal = _Signal
+    qtcore_module.QTimer = _QTimer
+    qtcore_module.QUrl = _QUrl
+    qtgui_module.QDesktopServices = _QDesktopServices
+    qtwidgets_module.QApplication = _Widget
+    qtwidgets_module.QLabel = _Widget
+    qtwidgets_module.QProgressBar = _Widget
+    qtwidgets_module.QVBoxLayout = _Widget
+    qtwidgets_module.QWidget = _Widget
+    qtwidgets_module.QPushButton = _Widget
+    qtwidgets_module.QHBoxLayout = _Widget
+
+    sys.modules["PySide6"] = pyside6_module
+    sys.modules["PySide6.QtCore"] = qtcore_module
+    sys.modules["PySide6.QtGui"] = qtgui_module
+    sys.modules["PySide6.QtWidgets"] = qtwidgets_module
 
 
 MODULE_PATH = Path("updater_gui.py")
+_install_pyside6_stubs()
 SPEC = importlib.util.spec_from_file_location("updater_gui_under_test", MODULE_PATH)
 updater_gui = importlib.util.module_from_spec(SPEC)
 SPEC.loader.exec_module(updater_gui)