Other applications' xdata on an entity was kept beside the drawing,
keyed by handle, so a copy (new handle) lost it: a copied hyperlink
(PE_URL) had no link, third-party tags stayed on the original only.
In AutoCAD xdata is part of the object.
Move entity xdata onto the entity as Common::xdata (the same raw
groups); every copy path already clones Common. The DXF reader puts it
there (handle references still noted for remapping), the writer takes
it from the entity, PDF hyperlinks come from the entities. EXPLODE's
pieces of an object don't inherit its xdata. Table record and block
xdata stay in Foreign.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
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