Faster tests: hostile_params_never_panic shares its commands across threads (154 s to 20 s), the design-file fuzz test tries its seeded cases on all cores (21 s to 7.5 s), the kernel's tangent-primitive boolean test runs its three seeds at once, and the headless scenario harness skips the software viewport render it threw away every frame (scenarios 63 s to 26 s). kill_mid_save waits for the saver to reach a varying round instead of sleeping a fixed time, so it holds on a busy machine

crates/ui-egui/src/scenario.rs

@@ -170,6 +170,8 @@ impl Harness {
     /// File pickers answer like a person would: save into the scenario's folder, open the file
     /// the scenario chose.
     fn install(&mut self) {
+        // Frames are laid out, never painted.
+        self.app.viewport.no_pixels = true;
         let dir = self.dir.clone();
         self.app.services.pick_save = Some(Box::new(move |name, _| Some(dir.join(name).to_string_lossy().into_owned())));
         let next = self.next_file.clone();