Fix: Handle coordinate bonds (bond order 8) from chython that caused IndexError during
retrosynthetic planning.
Certain molecules produced by the Reactor contained special/coordinate bonds (chython bond order
8), which crashed the graph featurization pipeline with index 7 is out of bounds for dimension 0
with size 3.
Added remove_coordinate_bonds() before canonicalization and kekulization across all molecule
processing entry points:
- mol_to_pyg() — graph conversion for policy network
- mol_from_smiles() / target_from_rdkit() — molecule input
- safe_canonicalization() — building block standardization
- apply_reaction_rule() — MCTS product validation
- reaction_rules_appliance() — training data preprocessing
- validate_rule() — rule extraction