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/modules/block_editor/mod.rs

@@ -94,6 +94,41 @@ impl CadModule for BlockEditorModule {
                     ),
                 );
             }
+            groups.push(RibbonGroup {
+                title: "Visibility",
+                tools: vec![
+                    RibbonItem::LargeTool(ToolDef {
+                        id: "BVSTATE_MANAGER",
+                        label: "Visibility States",
+                        icon: IconKind::Svg(include_bytes!("../../../assets/icons/ui/list.svg")),
+                        event: ModuleEvent::Command("BVSTATE DIALOG".into()),
+                    }),
+                    RibbonItem::Tool(ToolDef {
+                        id: "BVMODE_TOGGLE",
+                        label: "Visibility Mode",
+                        icon: IconKind::Svg(include_bytes!(
+                            "../../../assets/icons/constrain/show_all.svg"
+                        )),
+                        event: ModuleEvent::Command("BVMODE TOGGLE".into()),
+                    }),
+                    RibbonItem::Tool(ToolDef {
+                        id: "BVSHOW",
+                        label: "Make Visible",
+                        icon: IconKind::Svg(include_bytes!(
+                            "../../../assets/icons/constrain/show.svg"
+                        )),
+                        event: ModuleEvent::Command("BVSHOW".into()),
+                    }),
+                    RibbonItem::Tool(ToolDef {
+                        id: "BVHIDE",
+                        label: "Make Invisible",
+                        icon: IconKind::Svg(include_bytes!(
+                            "../../../assets/icons/constrain/hide_all.svg"
+                        )),
+                        event: ModuleEvent::Command("BVHIDE".into()),
+                    }),
+                ],
+            });
             groups
         })
     }

src/modules/draw/modify/bvstate.rs

@@ -66,7 +66,8 @@ impl CadCommand for BvStateCommand {
     fn prompt(&self) -> String {
         match &self.step {
             Step::Option => {
-                crate::t!("BVSTATE  Enter an option [New/Set/Rename/Delete] <Set>:").into_owned()
+                crate::t!("BVSTATE  Enter an option [New/Set/Rename/Delete/Dialog] <Set>:")
+                    .into_owned()
             }
             Step::NewName => crate::t!("BVSTATE  Enter name of new visibility state:").into_owned(),
             Step::SetName => crate::tf!(
@@ -93,6 +94,7 @@ impl CadCommand for BvStateCommand {
                 CmdOption::new(crate::t!("Set").as_ref(), "S"),
                 CmdOption::new(crate::t!("Rename").as_ref(), "R"),
                 CmdOption::new(crate::t!("Delete").as_ref(), "D"),
+                CmdOption::new(crate::t!("Dialog").as_ref(), "DIALOG"),
             ],
             _ => Vec::new(),
         }
@@ -114,6 +116,7 @@ impl CadCommand for BvStateCommand {
         match &self.step {
             Step::Option => {
                 self.step = match text.trim_start_matches('_').to_ascii_uppercase().as_str() {
+                    "DIALOG" => return Some(CmdResult::Dispatch("BVSTATE DIALOG".into())),
                     "N" | "NEW" => Step::NewName,
                     "" | "S" | "SET" => Step::SetName,
                     "R" | "RENAME" => Step::RenameFrom,
@@ -196,5 +199,5 @@ impl CadCommand for BvStateCommand {
 }
 
 inventory::submit!(crate::command::CommandRegistration {
-    names: &["BVSTATE", "BVHIDE", "BVSHOW"]
+    names: &["BVSTATE", "BVHIDE", "BVSHOW", "BVMODE"]
 });

src/modules/draw/select.rs

@@ -177,6 +177,10 @@ impl SelectObjectsCommand {
 }
 
 impl CadCommand for SelectObjectsCommand {
+    fn reveals_hidden_block_objects(&self) -> bool {
+        self.pending_cmd == "_BVSHOW"
+    }
+
     fn name(&self) -> &'static str {
         "SELECT"
     }