The verify step fetched the closure from Attic alone, but Attic's upstream-cache filter (cache.nixos.org-1) intentionally skips nixpkgs deps like sqlite, so `nix copy` failed on 'path is not valid'. Mirror the kiosk updater and fetch from Attic + cache.nixos.org together, Attic first so a truncated RadiantWave NAR still fails before the manifest is published.