Function register_plugin_option 

pub fn register_plugin_option(
    registry: &ConfigRegistry,
    name: &str,
    kind: PluginOptionKind,
    default: &str,
    doc: &str,
) -> bool

The register-option host-service body (PH7.10). Builds a concrete Option<bool|i64|String> from the plugin’s declaration and registers it into the SAME ConfigRegistry core options use. Returns false (registering nothing) if default doesn’t parse for kind OR name collides with an existing option — a plugin must not silently shadow another option.

The name-collision check runs BEFORE any string leak (below), so a rejected registration allocates nothing.