feat(xref): row-level context menu actions and unified split-button toolbar

Right-click actions bound to the row under the cursor, split-button toolbar groups with shared borders and hover states, and a notice when an operation needs a selection first.

locales/ru-RU/opencadstudio.ftl

@@ -3306,6 +3306,7 @@ insert =
     .revolve-select-objects-or-mode = REVOLVE  Выберите объекты для вращения или [Режим] (Enter — завершить):
 
     .path = Путь:
+    .xref-file-references = File References
 model =
     .create = Создание
     .boolean = Булевы операции