One core for "which libraries can this user see": family-lens default-
allow stays where it always was (the GetUserVisibleLibraries SQL);
the core adds the shared set+ids shaping that four endpoints each
hand-rolled. Media's visibleLibrarySet is now a thin identity adapter
(JWT user object -> resolved id) and the download-permission gate uses
the set instead of a manual membership loop.
Semantic diff (H4.5 step 1, in the plan): zero family-lens divergence
found across all six sites — the rule lives in one query; the variation
was shape-level (identity adapter, set-vs-ids, UUID idiom).
John O'Keefe
1d12a64915