Extend federation manifest schema for url sources with auth and TTL metadata.
Fetch remote capability indexes over HTTP(S), cache under
registry/federation/cache/, and fall back to stale cache on fetch failure.
Add --refresh flag, seven federation tests, and updated federation docs.
Register six new capabilities (12 total), add searchable catalog UI and graph
explorer, introduce pytest suite with CI fail-on-warnings, and close gap
analysis priorities 13 and 16. WP-0010 remains backlog for network federation.
