migrate pyqt5 to pyside6

apps/studio/src/orisys_studio/main.py

@@ -6,7 +6,12 @@ import logging
 import os
 import sys
 
-from PyQt5.QtWidgets import QApplication
+# pyqtgraph picks its toolkit from whichever binding is already imported, and in a
+# development environment that also has PyQt5 installed (``orisys[gui]``) it can pick the
+# wrong one. The application is PySide6-only, so say so before anything imports pyqtgraph.
+os.environ.setdefault("PYQTGRAPH_QT_LIB", "PySide6")
+
+from PySide6.QtWidgets import QApplication  # noqa: E402
 
 from orisys_app_shared import API_VERSION, __version__ as shared_version
 from orisys_app_shared.compat import check_shared_compat
@@ -85,7 +90,7 @@ def main() -> int:
         language,
         gl_profile,
     )
-    code = int(app.exec_())
+    code = int(app.exec())
 
     # Leave the process immediately.
     #