conditional os in UI xml, add system dialog file open on osx, check api format or error message when opening a document, per-char text wrap on NodeText, additional info on create doc dialog like working path

src/app_layout.cpp

@@ -389,7 +389,10 @@ void App::init_menu_file()
                 };
             if (auto b = popup->find<NodeButtonCustom>("file-open"))
                 b->on_click = [this](Node*) {
-                    dialog_open();
+                    //dialog_open();
+                    App::I.pick_file({"ppi","PPI"}, [this](std::string path){
+                       App::I.open_document(path);
+                    });
                     popup->mouse_release();
                     popup->destroy();
                 };