PluginAssets] inventory is at its source (the discovery
cache or the on-disk content) — the wire cap is reported separately via
the *Total fields.
Binary, deliberately: a discovery walk either enumerates a plugin’s
content to exhaustion or records nothing (abort-and-keep-previous), so
there is no partially-inventoried state for the wire to carry. The client
must never render a spinner for Unknown — it
will not resolve until the plugin’s content becomes enumerable.