A poster type registered by another plugin's bundle (upg100-list, by
my-upg-100-list.js) could only say No posters on a Poster Sections preset
page, which loads poster-sections.js alone. src/typeScripts.js names such
types and their bundles; the page adds the bundle as a second <script>, once
per page, when the type is not registered yet (the registry is one per page),
and re-resolves the type when its registration is announced, so all regions
lists the type's regions as they arrive. Copy embed carries the same second
script. The Configure picker offers these types before their script runs,
named from the catalogue (posterSections.typeUpg100List, 11 locales).
check:poster-sections: every preset's type is the library's own or listed in
src/typeScripts.js with its bundle in the built tree; its self-test proves a
preset whose type no script registers fails.
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