Sheet set row menus: own fly-out menu widget

The row menu is a small overlay widget: a click on a submenu entry opens
its fly-out instead of closing the menu, and the fly-out is placed beside
the menu where it actually landed (right when it fits, otherwise left), so
the menu never moves.

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

src/app/view/mod.rs

@@ -3041,7 +3041,7 @@ impl OpenCADStudio {
                 auto_collapse,
             ),
             crate::ui::dock::PanelId::SheetSetManager => {
-                crate::ui::window::sheet_set::view(&self.sheet_set, width, auto_collapse, side == crate::app::config::DockSide::Right)
+                crate::ui::window::sheet_set::view(&self.sheet_set, width, auto_collapse)
             }
         };
         let divider = dock_divider(id);