[cschanhniem]

Implements E7 from NEXT_100_PR_MAP.

What

• src/openamp_foundry/cli/commands/validate_packet.py: load_packet_from_json() reads ERP- JSON from disk; validate_packet_file() returns {valid, violations, packet_id, error}; _run_validate_packet() prints PASS/FAIL with violations; all parse helpers (_parse_candidate_entries, _parse_benchmark_summaries, etc.)
• tests/cli/test_validate_packet.py: 45 tests in 7 classes
• BASELINE: 8585 → 8648

Disconfirming pass

• No safety gates modified — this is a READ-ONLY validator
• dry_lab_only_attestation=False correctly produces FAIL (tested)
• empty limitations correctly produces FAIL (tested)
• Missing file returns exit code 1, not a crash
• Valid packet from examples/ structure passes