feat(registry): publish catalog structured data

[EmersonBraun]

Summary

• publish Organization, WebSite, CollectionPage, and SoftwareSourceCode JSON-LD for the Registry
• connect the public catalog to its canonical open-source repository and license
• verify the serialized graph with unit coverage and rendered production HTML

Validation

• pnpm --filter @agentskit/registry-app test
• pnpm --filter @agentskit/registry-app lint
• pnpm --filter @agentskit/registry-app build
• pnpm docs:bridge:gate
• git diff --check

No package release or changeset is required because this only changes metadata in the private Registry app.