Migrate UI framework from DearPyGUI to PySide6

[Copilot]

Replaces DearPyGUI with PySide6 (Qt) as the default UI framework. Core node editor functionality is complete; individual node implementations require adaptation in future work.

Implementation

Node Editor (node_editor/pyside6_node_editor.py)

• QGraphicsView-based canvas with QGraphicsScene
• GraphicsNode (QGraphicsItem) with input/output NodeSockets
• NodeConnection using QPainterPath for Bezier curves
• Export/import with validation

Main Application (main.py)

• Initializes node factories from directory (234 nodes discovered)
• Menu system populated dynamically by node type
• File I/O via QFileDialog
• Original DearPyGUI version preserved in main_dearpygui.py

Architecture

PySide6NodeEditor(QGraphicsView)
  └── QGraphicsScene
      ├── GraphicsNode(QGraphicsItem)
      │   ├── NodeSocket (input/output connection points)
      │   └── QGraphicsProxyWidget (for embedding Qt widgets)
      └── NodeConnection(QGraphicsPathItem)

Current State

Working:

• Node creation from menus
• Visual node positioning and connections
• Pan/zoom navigation
• Graph serialization

Phase 2 (not in this PR):

• Node instance integration with processing logic
• Parameter widgets (sliders, inputs, etc.)
• Data flow execution pipeline

Example Usage

# PySide6 (default)
python main.py

# Legacy DearPyGUI
python main_dearpygui.py

# Demo
python demo_pyside6.py

Files

• main.py - Now uses PySide6
• main_dearpygui.py - Original DearPyGUI implementation (backup)
• node_editor/pyside6_node_editor.py - Node editor implementation
• demo_pyside6.py - Demo script
• Documentation updated (README.md, PYSIDE6_MIGRATION_GUIDE.md, PYSIDE6_MIGRATION_SUMMARY.md)

Dependencies

requirements.txt already contained PySide6>=6.4.0; no dependency changes needed.

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