forked from 1b-agent/opencadstudio-upstream
OpenCADStudio/plugins#901 (comment) - Add BuiltinPlugin::on_load(&mut self, host: &mut dyn HostApi) with a default no-op implementation so existing plugins remain source-compatible. - Invoke on_load once for V4 plugins immediately after the runner connects and before entering the request loop, giving plugins a HostApi surface to cache plugin_request_sender() or set up worker threads before any dispatch. - V2/V3 plugins are unchanged: HostApi is only available during dispatch.