<posterverse-app> is a vertical-tab rail of whole poster plugins, each mounted
as its real element from the manifest: UPG 100 List Posters (upg-100-mfe),
Country Posters (country-posters-mfe), Poster Design, and an Experimental
folder of Wall of People Groups, All People Groups, UPG Neighbor and Bible
Posters. It reuses VerticalTabsLayout, loadScriptOnce/whenTagDefined and the
Research Gallery's profile-config contract (urlSync:false, mapTitle, token
ladder, treeBase, assetsBase).
The whole rail is an allow-list (src/tabs.js), so a gated plugin such as
key-cities can never appear. Rows whose bundle is not in the tree are pruned;
Poster Design and Bible Posters carry provisional ids until their bundles land.
meta.json declares nested-mfe-spa and composes the five rows that exist, so
the Plugin Studio lists it under capability 5.
check:posterverse-shelf (in gates:pre) asserts the allow-list, the key-cities
exclusion, composite-not-leaf resolution, composes/rail agreement and
11-locale string parity; --self-test plants one defect per arm.
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