Some DWGs written by other programs leave the root named-objects
dictionary unrecoverable: the header pointer names a non-dictionary and
the real NOD child dicts are owned by a table-control handle, so nothing
has owner==NULL. Navigating the root then silently no-ops, and
registering a new named-object entry (page setup, annotation scale, CTAB)
against the missing root orphans it — it never round-trips.
Add shared annotative::root_named_dict_handle(): resolve the header
pointer, else adopt the richest owner==NULL dict, else synthesise a fresh
root and write it back. Route ensure_plotsettings_dict, add_scale's
scalelist-create branch, and set_saved_active_layout through it. Resolve
the plot-settings dict via the PlotSettings owner when the header pointer
is stale, mirroring scalelist_dict_handle.
Verified page setups survive a DWG save/reload on the repro file with
layouts intact.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
