Bug: Stochastic %K division by zero on flat price — inf propagates past fillna into feature tensor

[bradsmithmba]

Summary

When price is constant over the stochastic window, highest_high - lowest_low == 0. The %K formula divides by zero, producing inf (not NaN). fillna(0) does not replace inf, so infinity enters the feature tensor, causing the RegimeDetector forward pass to produce NaN activations silently.

Evidence

src/features/regime_features.py line 239:

k_percent = 100 * (close - lowest_low) / (highest_high - lowest_low)

No zero guard. When flat: 0 / 0 for the numerator case produces NaN, but non-zero / 0 produces inf.
src/features/regime_features.py line 291: fillna(0) does not replace inf.

Fix

Add: k_percent = k_percent.replace([np.inf, -np.inf], np.nan).fillna(50.0) — default to midpoint (50) for flat price, which is the economically correct neutral value.