[BUG] Undo replaces MCQ with Conditional after edge deletion

[matKlju]

Bug description:
When adding an Assign node followed by a Conditional node, deleting the edge, undoing twice, then adding an MCQ node, deleting its edge, and undoing again, the MCQ node is incorrectly substituted with a Conditional node.

Expected behavior:
Undo/redo should restore the correct node types. An MCQ node must remain an MCQ and must not be replaced by a Conditional node.

mcq_undo_error.zip

Additional information:
Repro steps:

1. Add Assign
2. Add Conditional
3. Delete edge
4. Undo ×2
5. Add MCQ
6. Delete edge
7. Undo

Result: MCQ node is replaced with Conditional