PairEvaluator already computes OptimalRotation via RotatingCalipers on
the pair's convex hull, but PairFiller.EvaluateCandidate only passed
hull edge angles to FillPattern. Now includes the optimal rotation
angle (and +90°) so tiling can use the mathematically tightest fit.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>