fix(policy): resolve circular import blocking package import

[Rehan30g]

Summary

redactable.policy.engine imports Policy back from redactable.policy, but redactable/policy/__init__.py imports engine before it gets to defining/importing Policy itself. That circular reference means import redactable currently raises:

ImportError: cannot import name 'Policy' from partially initialized module 'redactable.policy' (most likely due to a circular import)

This isn't a corner case — it fails on a plain import redactable, and it was blocking pytest from even collecting test_apply.py, test_policy_engine.py, test_policy_loader.py, and test_transforms.py.

Fix

Import Policy directly from redactable.policy.model (where it's actually defined) instead of re-importing it through the package __init__.

Type

• Bug fix

Testing

• import redactable now succeeds.
• pytest tests/test_apply.py tests/test_policy_loader.py tests/test_transforms.py — all pass (these previously failed to even collect).
• ruff check src/redactable/policy/engine.py — clean.
• mypy src/redactable/policy/engine.py — clean.

Note: a few unrelated tests (test_detectors.py, test_pandas_integration.py, test_policy_engine.py's audit-event tests) fail for separate, pre-existing reasons (e.g. datetime.utcnow() deprecation warnings promoted to errors, and Finding attribute mismatches) that were previously masked by the collection error. Left those out of scope to keep this fix focused and easy to review.

Checklist

• Tests added/updated (existing regression coverage now actually runs)
• Docs updated (not applicable, internal import fix)
• Pre-commit hooks passed locally
• Lint/typecheck passed (ruff, mypy)
• Backwards compatible
• Changelog entry added