Three bugs fixed in NfpSlideStrategy pipeline:
1. NoFitPolygon.Reflect() incorrectly reversed vertex order. Point
reflection (negating both axes) is a 180° rotation that preserves
winding — the Reverse() call was converting CCW to CW, producing
self-intersecting bowtie NFPs.
2. PolygonHelper inflation used OffsetSide.Left which is inward for
CCW perimeters. Changed to OffsetSide.Right for outward inflation
so NFP boundary positions give properly-spaced part placements.
3. Removed incorrect correction vector — same-drawing pairs have
identical polygon-to-part offsets that cancel out in the NFP
displacement.
Also refactored NfpSlideStrategy to be immutable (removed mutable
cache fields, single constructor with required data, added Create
factory method). BestFitFinder remains on RotationSlideStrategy
as default.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Creates PolygonHelper.cs in OpenNest.Engine.BestFit with ExtractPerimeterPolygon
(returning PolygonExtractionResult with polygon + correction vector) and RotatePolygon.
AutoNester.ExtractPerimeterPolygon and RotatePolygon become thin delegates.
Adds MakeSquareDrawing/MakeLShapeDrawing to TestHelpers and 6 PolygonHelperTests.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
