The global context menu's single "Download example images" entry always
posted force=true, i.e. the re-process-all path that ignores the previous
run's state and re-checks every model. The per-model and bulk menus
already expose both choices, so the global entry was the odd one out.
Turn it into a submenu with "Download Missing" (force=false, keeps the
progress-aware skip) and "Re-process All" (force=true), both still
library-wide. The labels reuse the per-model submenu keys, which are
already translated in every locale, so no new i18n keys or placeholders
are introduced.