Viewport: silhouette outlines on curved surfaces (back faces pushed out on screen, drawn behind the model) in the styles with edges; new visual style Shaded with Hidden Edges (edges behind the model drawn faintly)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AS5Tn3xieewUSg3uxrMVdL

crates/ui-egui/src/prefs.rs

@@ -284,8 +284,8 @@ pub fn show(app: &mut SolveApp, ctx: &egui::Context) {
                             ui.checkbox(&mut app.ui.perspective, "");
                             ui.end_row();
                             ui.label("Visual style");
-                            let styles = ["Shaded with edges", "Shaded", "Wireframe"];
-                            egui::ComboBox::from_id_salt("pref_style").selected_text(styles[usize::from(app.ui.visual_style.min(2))]).show_ui(
+                            let styles = ["Shaded with edges", "Shaded", "Wireframe", "Shaded with hidden edges"];
+                            egui::ComboBox::from_id_salt("pref_style").selected_text(styles[usize::from(app.ui.visual_style.min(3))]).show_ui(
                                 ui,
                                 |ui| {
                                     for (i, s) in styles.iter().enumerate() {