Fix: Standardize Default Qt Binding Order to Prioritize PyQt

[idesign0]

📝 Summary of Change

This Pull Request standardizes the default Qt binding selection logic within python_qt_binding by removing the platform-specific check for macOS (Darwin).

The default binding order is now uniformly set to ['pyqt', 'pyside'] for all operating systems.

🐛 Problem Solved

Previously, the logic for macOS was restricted:

if platform.system() == 'Darwin':
    DEFAULT_BINDING_ORDER = ['pyside']
else:
    DEFAULT_BINDING_ORDER = ['pyqt', 'pyside']

This restriction caused GUI tools like rqt to fail on macOS if the PySide2 package was not found, even if PyQt was correctly installed:

ModuleNotFoundError: No module named 'PySide2'

The system was prevented from falling back to the available PyQt binding.

✅ Solution (Code Change)

The platform-specific conditional logic is replaced with the robust, standardized order:

DEFAULT_BINDING_ORDER = ['pyqt', 'pyside']

🧪 Testing

• Platform: macOS 13.6 — 26.1 (25B78), Apple M2
• Python Version: 3.11
• ROS 2 Distro: kilted (Source)
• Verification: rqt without import errors