pub fn discover_one(plugin_dir: &Path) -> Result<DiscoveredPlugin, String>Expand description
Parse a single explicitly-named plugin directory — the :plugin-load <path>
entry point (PL8.C). Unlike discover (which scans a tree and silently
skips non-plugin subdirs), this is a direct request for one dir, so a
missing manifest is an error the user sees, not a silent skip.