Harden public asset verification

[ael-dev3]

Summary

• harden release verification against unsafe paths, special files, filesystem races, bounded-resource violations, and malformed archives
• make manifest trust explicit and require checksum sidecars
• add a private vulnerability-reporting policy plus exact-SHA-pinned Verify and CodeQL workflows
• expand regression coverage for filesystem, archive, checksum, and compressed-asset boundaries

Verification

• 32 Python tests pass with resource warnings treated as errors
• all 15 committed release manifests validate against the 21 published attachments
• deterministic title manifest rebuild matches the committed bytes
• current tree and full repository history pass redacted Gitleaks scans
• independent focused review found no remaining actionable issues

This changes repository verification and review controls only. It does not change, replace, or republish any release asset and does not touch the live Warpkeep application or database.

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