PXR Structure challenge ligands: Boltz2 no-MSA vs MSA aligned structures

Each ligand has two PDBs:
- assets/nomsa_aligned_to_msa/<ligand>.pdb: no-MSA top1 CA-aligned into the MSA top1 frame
- assets/msa_reference/<ligand>.pdb: MSA top1 reference frame

Top1 on both sides is best-of-25 by ligand/protein-ligand iPTM.
