0.21.0: eight full catalogues

Every film and every video game on Wikidata (CC0), every team and every player TheSportsDB knows (players as OpenProfile.md people with their socials), every anime on Kitsu, Project Gutenberg's whole catalogue, every LibriVox audiobook, and every app on Steam through the keyless store query. Each walk is capped per run, resumes from its cursor and states its licence. Built one agent per source and adversarially reviewed before integration. Also fixes the OpenSaaS route test that had kept main's CI red since 0.18.0.