feat(hashing): add policy tree hash helpers

[aa-parky]

Summary

• add deterministic policy file/tree hashing helpers for canonical policy workflows
• add directory subtree hash helper output for drill-down status views
• export new hash helper types/functions from package root
• add unit coverage for determinism, order independence, and directory hash stability

Validation

• ruff check pipeworks_ipc tests
• black --check pipeworks_ipc tests
• pytest -q

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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