AutoCAD writes handles above 2^48 (whole drawings whose handles start at 0xDAD1...).
dxf_raw dropped every foreign object with such a handle, so these drawings lost their
dynamic blocks and all other unmodelled objects on read, DXF to DXF as well. DXF handles
are up to 16 hex digits; the whole 64-bit range is now believed (null still is not).
Modelled entities and table records already accepted such handles.
Test: the DOOR fixture with every handle moved above 2^48 keeps its dynamic block
through a save (red before the change).
Co-Authored-By: Claude Opus 5.5 <[email protected]>
