Add patch for NodeGraphQt PySide6 6.7+ compatibility

The setSelectionArea() API changed in PySide6 6.7 - it now requires
an ItemSelectionOperation parameter before ItemSelectionMode.

Files added:
- patches/nodegraphqt_pyside6_compat.patch: Git-style patch file
- patches/UPSTREAM_ISSUE.md: Issue report for upstream project
- scripts/patch_nodegraphqt.py: Script to auto-apply the patch

The patch fixes rubber band selection errors when dragging in the
node graph viewer. Run after pip install:

    python scripts/patch_nodegraphqt.py

Co-Authored-By: Claude Opus 4.5 <[email protected]>

patches/nodegraphqt_pyside6_compat.patch

@@ -0,0 +1,13 @@
+--- a/NodeGraphQt/widgets/viewer.py
++++ b/NodeGraphQt/widgets/viewer.py
+@@ -521,8 +521,10 @@ class NodeViewer(QtWidgets.QGraphicsView):
+                 path = QtGui.QPainterPath()
+                 path.addRect(map_rect)
+                 self._rubber_band.setGeometry(rect)
++                # PySide6 6.7+ requires ItemSelectionOperation parameter
+                 self.scene().setSelectionArea(
+-                    path, QtCore.Qt.IntersectsItemShape
++                    path, QtCore.Qt.ReplaceSelection,
++                    QtCore.Qt.IntersectsItemShape
+                 )
+                 self.scene().update(map_rect)