Returns a single plugin entry for the given id.
If version is omitted, returns the latest.
Fails if the plugin or version is not found.
Optionalversion: stringReturns all registry plugins (latest version of each).
Returns all known versions of a plugin, identified by its composer plugin id (NSID). Ordered newest-first. Must return at least one entry.
Abstraction over the plugin registry catalog backend. Implementations may call Edge, a local cache, or a stub.
The interface itself is transport-agnostic; concrete implementations live alongside it in this package (see EdgeRegistryPluginProvider) so we avoid
app-framework ↔ edge-clientcycles, but they only need to satisfy this shape — callers can substitute their own.