feat: ignition opening with cold start, lamps, crossfade and shader warm-up

tests/browser/visual-regression.spec.ts

@@ -55,6 +55,13 @@ const waitForRenderedPortfolio = async (
     "data-scene-state",
     "running",
   );
+  // IGNITION: the first frame is cold and the canvas crossfades in; wait for
+  // the first frame (data-lit), the end of the ignition and the fade.
+  await expect(page.locator(".journey-canvas[data-lit]")).toHaveCount(1);
+  await expect(page.locator("html:not([data-ignition])")).toHaveCount(1, {
+    timeout: 10_000,
+  });
+  await expect(page.locator(".journey-canvas")).toHaveCSS("opacity", "1");
 };
 
 const captureViewport = async (