Results: a static step first shows its contours undeformed

The first look at a solved static step draws the von Mises contours on the
true geometry; the deformed shape comes when asked for (Deformed,
results.deformed, results.animate), at the automatic scale. Frequency steps
still open on mode 1 deformed and explicit steps at true scale, as the
owner's notes in #77 ask; a 0.24 mm deflection drawn as 10 mm no longer
reads as a failed part.

Fixes #77

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

crates/engine/src/view.rs

@@ -266,7 +266,8 @@ mod tests {
         s.execute("solve.static", &json!({})).unwrap();
         let (plot, shown) = render_png(&s, &iso, 64, 48, &Palette::LIGHT).unwrap();
         assert_ne!(model, plot);
-        assert!(shown.scale > 0.0 && shown.step.is_some(), "{shown:?}");
+        // A static step first shows its contours on the undeformed shape.
+        assert!(shown.scale == 0.0 && shown.step.is_some(), "{shown:?}");
         let (field, min, max) = shown.contour.unwrap();
         assert_eq!(field, "von_mises");
         assert!(max.1 > min.1);