Replaces PartBoundary polygon edges with PartGeometry.GetOffsetPerimeterEntities
(inflated Line/Arc entities) so arcs are handled exactly without the polygon
sampling error that previously required a bboxDim + PartSpacing clamp. Adds
bbox DirectionalGap / PerpendicularOverlap early-outs to skip pair checks
that can't produce a valid slide, and removes the now-unused PartBoundary
cache, GetPatternLines/GetOffsetPatternLines helpers, and ComputeCopyDistance
clamp.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>