Private copies of tolerant box containment, box union, vector rotation and
the cutout proposals' coordinate-range check now use one helper each:
BoundingBox.IsWithin and BoundingBox.Union, Vector.Rotate, and
CutoutCoordinates.WithinRange. Tests pin the helpers bit-for-bit against
frozen copies of the removed bodies. No behavior change.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>