Prototype policy engine for organization-wide rules #26

Summary

Investigate a policy engine that enforces org-level rules like "block Python 3.13 until date X" or "security-only during freeze" across all runs.

Why

Central policy control is a key differentiator for large organizations. Integrating policy checks into the action (or future GitHub App mode) enables consistent governance without manual intervention.

What needs to happen

• Define policy schema (YAML/JSON) covering version constraints, freeze windows, security gates, etc.
• Implement a policy evaluator invoked before rewrites occur.
• Provide example policies and documentation.
• Ensure policies can be sourced from the repo or a central location.
• Add tests for policy evaluation, overrides, and failure modes.

References

• Roadmap v2.0 idea: "Policy engine".

Acceptance criteria

• Prototype demonstrates enforcing at least two policy types (date-based freeze and security-only mode).
• Documentation explains configuration and precedence.
• Tests cover successful enforcement and override scenarios.