OpenCADStudio/plugins#901 (comment)
- Add HostApi::document_path(tab_id) returning Option<PathBuf>.
- Add PluginRequest::DocumentPath and PluginResponse::DocumentPath for
out-of-process plugins.
- Implement the request in the IPC server and in both V3/V4 plugin-side
HostApi proxies.
- Implement HostSession::document_path by looking up the tab by id and
returning its current_path.
Sync current main and companion codec changes before preserving unsupported frame rows, rendering in the entity plane, and sharing final layout metrics with placement preview.