SpaceMouse test: make the app before the reading, which goes stale on a slow runner (#1711)

Thanks @phanoob.

apps/solidcraft/src/space_mouse.rs

@@ -486,6 +486,9 @@ mod tests {
     #[test]
     fn each_frame_hands_the_view_its_motion_through_the_drivers_mapping() {
         // The reader's latest tilt, and a profile that makes tilt roll: the frame's motion rolls.
+        // The app is made first: on a slow runner that takes longer than a reading stays fresh.
+        let mut app = SolveApp::new(solidcraft_engine::Session::default(), solidcraft_ui_egui::Services::default());
+        app.home.open = false;
         let now = Instant::now();
         let mut reading = Reading::new(now);
         reading.axes.rotation = [0, 350, 0];
@@ -497,8 +500,6 @@ mod tests {
             wheel: WheelGuard::default(),
             started: now,
         };
-        let mut app = SolveApp::new(solidcraft_engine::Session::default(), solidcraft_ui_egui::Services::default());
-        app.home.open = false;
         mouse.tick(&mut app, &Context::default());
         let DeviceMotion { motion, seconds } = app.viewport.device_motion.expect("the frame hands the page its motion");
         assert_eq!(motion, Motion { translation: [0.0; 3], rotation: [0.0, 0.0, -1.0] });