The tensor-based log_probs() had an inverted sign on the squared
difference term: .sub(&(x * -0.5)) = +0.5*x² instead of -0.5*x².
This caused actions far from the mean to get higher log probabilities.
Also fix test assertions: continuous log probability densities CAN
be positive (when σ is small and action is near mean), unlike
discrete log probabilities which are always <= 0.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
37d6a15fc3