Resource suggestion: PolicyStrata for governed Text2SQL testing

## Resource

[PolicyStrata](https://github.com/raintree-technology/policystrata) is an MIT-licensed, deterministic regression-testing framework for cross-layer policy drift in LLM data-agent stacks.

It is aimed at text-to-SQL agents, BI copilots, semantic models, and governed analytics systems. It checks whether policy remains consistent across model-visible tools, semantic validation, SQL compilation, PostgreSQL controls, and result release, then writes a minimized witness identifying the first failed responsibility.

This is not a text-to-SQL accuracy benchmark or an authorization boundary. A possible placement would be **Libraries**, **Practice Projects**, or a testing/evaluation subsection if one is planned.

The project is available on [PyPI](https://pypi.org/project/policystrata/) and includes a reproducible paper artifact and a no-API-key demo via `uvx policystrata demo`.

I maintain PolicyStrata and am disclosing that relationship with this suggestion.

Review the existing Libraries, Practice Projects, and any testing or evaluation sections to determine the best placement for this resource. Add the PolicyStrata link and concise description in the selected section, preserving the repository's listing style and the maintainer disclosure.

Written by the indexing model from the issue text.