fix: prevent PushBoundingBox from making obstacles invisible to geometry push

PushBoundingBox left exactly partSpacing between bounding boxes, but the
geometry push inflates offset lines by halfSpacing + chordTolerance per
side (totaling partSpacing + 2*chordTolerance). The 0.002 overlap caused
RayEdgeDistance to return MaxValue for negative t, making the nearest
obstacle invisible and allowing the part to push through it.

Subtract 2*ChordTolerance from the BB push distance so the gap is wide
enough for the offset geometry lines to remain non-overlapping.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

OpenNest/Actions/ActionClone.cs

@@ -154,11 +154,9 @@ namespace OpenNest.Actions
                     default: hDir = PushDirection.Left; vDir = PushDirection.Down; break;
                 }
 
-                // Phase 1: BB-only push to get past irregular geometry quickly.
                 Compactor.PushBoundingBox(movingParts, plateView.Plate, hDir);
                 Compactor.PushBoundingBox(movingParts, plateView.Plate, vDir);
 
-                // Phase 2: Geometry push to settle against actual contours.
                 Compactor.Push(movingParts, plateView.Plate, hDir);
                 Compactor.Push(movingParts, plateView.Plate, vDir);