forked from 1b-agent/opencadstudio-upstream
The DXF reader keeps marker identities on the block record but never materializes the entities, so block_entity_handle/block_end_handle dangle after every DXF load (reopened baked *D dimension blocks hit this every time). Re-create missing sentinels at load finalize, reusing the file handle when free and minting otherwise. Idempotent and DWG-safe: loads whose markers already resolve are untouched. Pinned by dimlinear_survives_save_reload_with_baked_geometry.