* Fillet/chamfer: point the drag arrow into the corner on inside edges (#1384)
The radius/distance arrow always pointed against the faces' outward
bisector, which is into the body on an outside edge but away from the
corner on an inside one, where the blend adds material. The arrow and
the spline radius handles now take each edge's convexity into account,
so dragging out along the arrow grows the value on both kinds of edge,
and each edge of a mixed chain follows its own.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
* Tests: no unreachable! in the blend arrow helper
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
