Add tool authorization drift review skill

[xiefuzheng713-alt]

/claim #259

Summary

• Add a new tool-authorization-drift AI-security/auth skill for agentic tool policy/runtime mismatch reviews.
• Cover declared-vs-runtime capability mapping, preview/execute confusion, delegated calls, stale approval caches, alias canonicalization, worker re-checks, and audit evidence.
• Include README, pattern references, YAML/Python vulnerable fixtures, YAML/Python benign fixtures, and index registration.

Validation

• git diff --check
• git diff --cached --check
• required frontmatter check across skills/ and roles/
• index.yaml listed-file existence check
• skill_count consistency check
• prompt-injection pattern scan equivalent to the repository workflow
• python -m py_compile for the new Python fixtures, with generated cache files removed before commit
• PyYAML safe_load for the new YAML fixtures

Safety

• Defensive review guidance only.
• Synthetic fixtures only.
• No credentials, private keys, tokens, cookies, real customer data, payment credentials, or external API calls.

Closes #259