🎯 What does this PR do?

• Add a table-driven test that enumerates every registered tool and resolves its outputSchema, proving JSON Schema 2020-12 compliance in CI.
• Add README section describing structured output behavior.

✅ Checklist

• My code follows the style guidelines of this project.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation (if needed).
• My commit messages follow the Conventional Commits standard.