## Summary

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## Parity Impact Statement

Describe any Lean/Rust encoding or behavior parity impact:

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## Checklist

- [ ] I updated `docs/19_rust_lean_parity.md` for changed parity surfaces.
- [ ] I provided a parity impact statement above.
- [ ] I added/updated tests for behavior changes.
- [ ] If I introduced a justified break, I added a deviation entry to the Deviation Registry in `docs/19_rust_lean_parity.md`.
