feat(ribbon): contextual Block Editor tab while editing a block

Opening the block editor brings up a Block Editor ribbon tab with
Edit / Save / Discard, Attribute Definition, and the geometric,
dimensional and parameter tools that drive parametric blocks. The tab
is only listed while a block editor session is open, and leaving the
session returns to the tab that was active before.

Refs #509

Co-Authored-By: Claude Opus 5.5 <[email protected]>

locales/ru-RU/opencadstudio.ftl

@@ -29,6 +29,7 @@ action =
     .plugins = Модули
 
 ribbon-tab =
+    .block-editor = Редактор блоков
     .draw = Начертить
     .parametric = Параметрический
     .annotate = Аннотации