v0.3.0

Structure quality metrics (Slice C).

Added

• MolProbity-style Ramachandran classification (favored / allowed / outlier; Gly/Pro regions)
• Steric clash detection (heavy atoms, configurable VdW overlap)
• Missing backbone checks (N, CA, C, O) for canonical and common variant residues
• CLI: quality <input> — per-residue JSONL (problems only by default; --all-residues for full output)
• Structure-level quality fields in featurize: quality_residue_count, Ramachandran counts, clash_pair_count, missing_backbone_residue_count
• --clash-overlap on featurize and quality (default 0.4 Å)

See CHANGELOG.md for full details.