SIG audit loop

1. Run sig-audit and select one weak property.
2. Identify a bounded structural change with a measurable expected effect.
3. Measure before, implement, and measure after with identical settings.
4. Keep the change only when the target improves and verification remains green.
5. Repeat until the target is met or further changes have no credible benefit.
6. Run review before proposing the final result.

Never combine unrelated cleanup into one measurement iteration.