Thickness (DXF 39) is a General-group property in the palette, but it is
stored per-entity, so it was previously shown (inconsistently) only in the
Geometry section of a few entities. Surface it in General for every entity
type that carries an extrusion thickness (arc, circle, line, lwpolyline,
point, polyface mesh, 2D polyline, shape, 2D solid, text) via
entity_thickness / set_entity_thickness, routed through apply_common_prop.
Removes the now-duplicate Thickness rows (and dead apply arms) from the
arc/circle/shape/solid Geometry sections so it is never shown twice.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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