fixed test env on windows

Author: plasmax

AGENTS.md

@@ -18,3 +18,11 @@ This repo already has Qt binding coverage. Avoid opening heavy files unless need
 ## Test commands
 - PySide6: `.\.venv\Scripts\activate.ps1; $env:QT_PREFERRED_BINDING="PySide6"; pytest -vv`
 - PySide2: `.\.venv\Scripts\activate.ps1; $env:QT_PREFERRED_BINDING="PySide2"; pytest -vv`
+
+## Python/venv notes (Windows)
+- If `.venv\Scripts\python.exe` prints `No Python at ...Python310\python.exe`, the venv is stale and was created against a removed interpreter.
+- Python 3.13 cannot install pinned `PySide6==6.5.2` from `requirements-pyside6.txt` (no wheel for 3.13).
+- Working fallback on Python 3.13:
+  - `python3 -m venv .venv`
+  - `.\.venv\Scripts\python.exe -m pip install PySide6 shiboken6 Qt.py six pytest`
+  - `.\.venv\Scripts\activate.ps1; $env:QT_PREFERRED_BINDING="PySide6"; pytest -vv`