[cschanhniem]

Summary

• Added baseline_caveat field to build_certificate() in certificate.py
• Auto-computes three canonical cheap-baseline flags: charge≥4 (cationic bias), length 10-40aa (typical AMP range), hydrophobic_fraction≥0.30
• When all three flags pass, warns: 'simple conjunction rule would select this candidate without ML scoring — residual ML signal must exceed this baseline'
• Partial-pass and no-pass cases get calibrated notes
• 63 tests covering: field presence, charge/length/hydrophobicity flag logic, boundary cases, all-YES path, all-NO path, claim discipline (no biological overclaims), JSON roundtrip, integration with other cert fields
• BASELINE 6331→6394
• Closes Phase B B3 — cheap-explanation visibility is now mandatory at certificate issue time, not just reviewer convention