-`community/` - community plugin source folders. These are installable plugins, but they are not preinstalled unless a registry entry points at them and the user installs one.
-`registry/` - default registry source manifests (`open-design-marketplace.json`) for official and community catalogs. These feed the Plugins Available/Sources UI.
-`spec/` - the portable plugin specification, templates, examples, and agent handoff kit for building, testing, publishing, or opening a PR back to OpenDesign.
The common contract is the same everywhere: a plugin is a portable agent skill folder with a `SKILL.md`, plus an optional versioned `open-design.json` sidecar that gives OpenDesign marketplace metadata, inputs, previews, pipelines, and trust/capability hints.