- Correctness (stale HU): _sync_overlay is now a full reconcile — it clears every guid-bearing EN
row's *_hu first, then repopulates the matches, so a title whose HU twin vanished or was re-guid'd
falls back to EN instead of keeping stale Hungarian metadata (only rows that held HU data go dirty).
- Correctness (dup guid): by_guid maps a guid to the LIST of EN rows carrying it, so two editions of
one film both receive the overlay instead of just the last-iterated one.
- Robustness (guid wipe): _apply_item/_sync_shows keep a prior guid when a listing carries none
(`_canonical_guid(meta) or row.guid`), so a server ignoring includeGuids can't erase the match key.
- Reuse: merged _sync_overlay's movie/show branches (only the select + item_type differ).
- Test-coverage: a full-sync test drives sync() over a stub Plex (sections + section_items +
overlay_map) asserting pass-2 designation (metadata_lang/overlay_of), guid capture, the HU write,
and browse exclusion; plus a reconcile test that a vanished twin clears stale *_hu.
Full backend suite 274 passed / 2 skipped.
peter
704c6c35d4