feat(block-editor): add functional Visibility ribbon controls

Add the current-state selector, Visibility States dialog and mode/show/hide
controls to the contextual ribbon, using shared icons, tooltips, modal UI
and adaptive flyouts. Disable the controls until a Visibility parameter exists.

Stage state creation, rename, deletion, current-state changes and reordering
until OK. Support copied, show-all and hide-all new states in one undo step,
preserve native graph metadata, and restore current-state identity on undo/redo.

Implement nonsaved BVMODE and display-only reveal during BVSHOW selection.
Cancelling selection leaves saved visibility flags and history unchanged.
Keep the existing command-line state workflows available.

Validation: 6 targeted tests; 277 block, 31 app dock, 35 ribbon and 12 history
checks passed (overlapping filters). All 17 local DWG fixtures passed in-memory
DWG/DXF preservation checks with unchanged original checksums.

src/app/update/command.rs

@@ -1254,7 +1254,7 @@ impl OpenCADStudio {
         }
     }
 
-    pub(super) fn on_command_escape(&mut self) -> Task<Message> {
+    pub(in crate::app) fn on_command_escape(&mut self) -> Task<Message> {
         self.tabs[self.active_tab].measurement.clear();
         // Escape answers a pending client getpoint request first: no point.
         if self.control.get_point.is_some() {