[cschanhniem]

Implements E1 from NEXT_100_PR_MAP: external review packet Python module.

What

• external_review_packet.py: ExternalReviewPacket + CandidateEntry + BenchmarkSummary + CalibrationSummary + SafetyAttestations + PacketValidationResult
• validate_external_review_packet(): 14 validation rules, dry-lab proof_ladder_level cap at 2
• format_external_review_packet(): human-readable output with VALID/INVALID status
• Key safety gates: dry_lab_only_attestation must be True, no_known_toxicity_claim must be True, limitations required
• 63 tests; BASELINE 7339 to 7402

Why

The JSON schema for ERP- packets already existed but no Python module enforced it. Without Python-level validation, a review packet could be sent to external reviewers with dry_lab_only_attestation=False or proof_ladder_level=5 — both of which misrepresent what the dry-lab pipeline can claim.

Disconfirming pass

• Cheapest explanation: schema alone is not enforcement; a Python validator that raises no error on bad data is worthless. These tests catch the specific misrepresentations that matter.
• Hidden certainty: proof_ladder_level > 2 for dry-lab artifacts is now blocked, not just warned.
• No safety/release policy changed; no calibration policy touched.