Add TealTiger - deterministic AI governance with SARIF export for CI/CD

[nagasatish007]

Adding TealTiger to the Testing section.

TealTiger is an open-source deterministic governance engine for AI agents with DevSecOps integration:

• Secret Detection: 500+ patterns across 9 categories (API keys, tokens, credentials)
• CI/CD Integration: GitHub Action (agentguard-ai/tealtiger-action@v1) for automated scanning
• SARIF Export: Upload results to GitHub Code Scanning
• Policy Testing: Golden test runner with JUnit XML for CI gates
• Zero Infrastructure: Runs as npm/pip package or Docker sidecar — no servers needed

DevSecOps-relevant features:

• Deterministic — same input + same policy = same decision (auditable, reproducible)
• Fail-closed defaults — broken guardrails don't become open doors
• Apache 2.0 licensed, actively maintained

GitHub: https://github.com/agentguard-ai/tealtiger
Action: https://github.com/agentguard-ai/tealtiger-action
npm: https://www.npmjs.com/package/tealtiger