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/lib.rs

@@ -300,7 +300,7 @@ impl SolveApp {
             self.autosave_minutes = m.clamp(0.0, 600.0);
         }
         if let Some(s) = v.get("visual_style").and_then(Value::as_u64) {
-            self.ui.visual_style = u8::try_from(s.min(2)).unwrap_or(0);
+            self.ui.visual_style = u8::try_from(s.min(3)).unwrap_or(0);
         }
         // Browser folders the user opened or closed.
         let keys = |k: &str| -> std::collections::BTreeSet<String> {