UI: a setup checklist at the top of the browser

Once a model has geometry or a mesh, the browser shows the analysis stages from the engine's
checklist, each ticked, next, dashed (optional) or open; a click starts the stage's command and a
blocked stage's hover says what it waits for. The × hides it and View › Setup checklist shows it
again; the choice is kept in the per-user prefs.json.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo

crates/ui-egui/src/viewport.rs

@@ -535,6 +535,7 @@ fn nav_bar(app: &mut ModelApp, ui: &mut egui::Ui, rect: Rect, t: &Tokens) {
             ui.checkbox(&mut app.ui.show_interactions, "Interactions");
             ui.separator();
             ui.checkbox(&mut app.ui.show_tree, "Browser");
+            ui.checkbox(&mut app.ui.show_setup, "Setup checklist");
             ui.checkbox(&mut app.ui.show_timeline, "Timeline");
         });
     }