fix: prevent division by zero in price_retracement_percent when prior range collapses

fix: prevent division by zero in price_retracement_percent when prior range collapses

- Replace linear price change calculations with log-space formulas in top_change_percent, bottom_change_percent, and price_retracement_percent
- Add masked division with np.isclose() guard in price_retracement_percent to handle flat prior windows (returns 0.0 when denominator ≈ 0)
- Migrate zigzag amplitude and threshold calculations to log-space for numerical stability
- Remove normalization (x/(1+x)) from zigzag amplitude and speed metrics (now unbounded in log units)
- Update %-close_pct_change feature from pct_change() to log().diff() for consistency
- Bump version to 3.10.10