feat(select): invert selection from the right-click menu

Add an Invert Selection entry to the selection context menu (below
Select Similar): it replaces the current selection with every other
selectable object in the active layout. Candidates come from the visible
wire set, so objects on off/frozen layers stay excluded.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/mod.rs

@@ -1289,6 +1289,9 @@ pub enum Message {
     /// Extend the current selection with every entity in the active
     /// layout that matches a selected entity by (type, layer).
     SelectSimilar,
+    /// Replace the current selection with every other selectable object in
+    /// the active layout (the complement of what's selected now).
+    InvertSelection,
     /// Keyboard modifier state changed — tracks whether Shift is held so the
     /// pick path can do subtractive (Shift+click) selection.
     SetShiftDown(bool),

src/app/update.rs

@@ -4971,6 +4971,16 @@ impl OpenCADStudio {
                 Task::none()
             }
 
+            Message::InvertSelection => {
+                let i = self.active_tab;
+                self.tabs[i].scene.selection.borrow_mut().context_menu = None;
+                let count = self.tabs[i].scene.invert_selection();
+                self.command_line
+                    .push_output(&format!("Invert Selection: {} object(s) selected.", count));
+                self.refresh_properties();
+                Task::none()
+            }
+
             Message::QSelectOpen => {
                 let i = self.active_tab;
                 self.tabs[i].scene.selection.borrow_mut().context_menu = None;

src/app/view.rs

@@ -2907,6 +2907,10 @@ fn viewport_context_menu_overlay(
             ));
             items.push(sep());
             items.push(item("Select Similar".to_string(), Message::SelectSimilar));
+            items.push(item(
+                "Invert Selection".to_string(),
+                Message::InvertSelection,
+            ));
         }
         if isolation_active {
             items.push(item(

src/scene/mod.rs

@@ -4896,6 +4896,27 @@ impl Scene {
         added
     }
 
+    /// Replace the selection with its complement: every selectable object
+    /// in the active layout that isn't currently selected. The candidate
+    /// set is the visible wire set, so objects on off/frozen layers (which
+    /// can't be picked anyway) are excluded. Returns the new count.
+    pub fn invert_selection(&mut self) -> usize {
+        let prev: rustc_hash::FxHashSet<Handle> = self.selected.iter().copied().collect();
+        let all: Vec<Handle> = self
+            .entity_wires()
+            .iter()
+            .filter_map(|w| Self::handle_from_wire_name(&w.name))
+            .collect();
+        self.selected.clear();
+        for h in all {
+            if !prev.contains(&h) {
+                self.selected.insert(h);
+            }
+        }
+        self.bump_selection();
+        self.selected.len()
+    }
+
     /// Replaces (or extends, when `append` is true) the current
     /// selection with every entity in the active layout that matches
     /// the filter. Returns the number of newly-matching entities.