The web save path discarded the chosen format version (`let _ = version`)
and `save_to_bytes` never applied it, so every browser download was
written at the document's default version (AC1032 / DWG 2018) regardless
of the format picked in the Save dialog. (#122)
Thread `version` into `save_to_bytes` and set `doc.version` there, the
byte-buffer counterpart to `save_as_version`. Saving as DWG 2013 now
writes an AC1027 file.
Co-Authored-By: Claude Opus 4.8 <[email protected]>