Add prod-like v3 corrected evidence brief

[InfoSecHack]

Summary

• Add a reviewer-facing evidence brief for the frozen corrected prod-like v3 IAMScope validation slice.
• Summarize the bounded sandbox lifecycle, v3 collection facts, comparator result, and cleanup evidence.
• Preserve explicit non-claims: no broad correctness, no production readiness, no exploitability proof, no composite score, and no pass/fail benchmark label.

Validation

• Targeted grep for key result numbers and non-claims
• Account/ARN hygiene scans: clean
• Terraform/raw artifact scan: clean
• ./scripts/check.sh: passed
• ./scripts/test_fast.sh: 1999 passed
• git diff --check: passed