feat(release): verify acceptance gate evidence

[mrnicholasbcarter-code]

Summary

• add a canonical fail-closed verifier for all G1-G7 acceptance criteria
• validate evidence paths, symlinks, duplicate keys, canonical JSON, and non-pass statuses
• document the machine-readable release gate contract and add focused tests

Issue

Closes #114

Verification

• python -m pytest -q tests/test_verify_gates.py tests/test_proof_matrix.py
• ruff check scripts/verify_gates.py tests/test_verify_gates.py
• mypy scripts/verify_gates.py --strict
• commit hook: Ruff, format, strict mypy
• pre-push hook: full test and security gates

[github-actions]

📊 Benchmark Results

coding

Metric	Fixed	Verdict	Delta
Success Rate	100.0%	98.5%	-1.5%
Cost/req	$0.014014	$0.007116	49.2%
p95 Latency	148ms	145ms	-3ms

reasoning

Metric	Fixed	Verdict	Delta
Success Rate	100.0%	98.0%	-2.0%
Cost/req	$0.007366	$0.004398	40.3%
p95 Latency	148ms	145ms	-3ms

chat

Metric	Fixed	Verdict	Delta
Success Rate	100.0%	98.0%	-2.0%
Cost/req	$0.000104	$0.001340	-1188.5%
p95 Latency	73ms	142ms	69ms