Test drawings used CCW winding, causing OffsetSide.Left to produce
inward offsets. The BestFit pipeline then positioned pairs so actual
shapes overlapped, failing all 1232 candidates. Changed to CW winding
to match CNC convention where OffsetSide.Left = outward.
Also fixed EdgeStartSequencer test: centerPart at (25,55) was only 4.5
from the top edge (plate Y=60), closer than midPart at (10,10). Moved
to (25,25) for correct ordering.
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>
Renamed OpenNest.Engine.Tests → OpenNest.Tests (directory, .csproj,
namespaces in all .cs files). Added OpenNest.IO project reference.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
