Even timesteps use the existing directional mirror (Short<->Long, negated
reward). Odd timesteps substitute a different magnitude and linearly scale
the reward by alt_mag_frac / actual_mag_frac, giving the magnitude branch
direct gradient signal about what bigger or smaller positions would have
earned. Falls back to directional mirror when reward is near-zero (scaling
uninformative). No extra buffer needed -- reuses the existing N*L
counterfactual slot.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
81538081bc