Add more built-in security patterns

[NeuZhou]

Good First Issue

Help expand ClawGuard's built-in security pattern library.

Areas Needing More Patterns

• Cloud provider secrets — Azure SAS tokens, GCP service account keys
• Container escape — Docker socket access, privileged container detection
• Steganography — Detecting data hidden in images/files via tool calls
• Browser automation abuse — Cookie theft, session hijacking via browser tools

How to Contribute

1. Fork the repo
2. Add patterns to \src/rules/\ in the appropriate category
3. Each pattern needs: regex, severity, description, and a test case
4. Run
   pm test\ to verify
5. Submit a PR

See \CONTRIBUTING.md\ for the full guide.