Resize

boot does not subscribe to window resize. Wire it explicitly:

globalThis.addEventListener("resize", () => {
  app.render.resize(globalThis.innerWidth, globalThis.innerHeight);
});

render.resize(w, h) calls camera.resize(w, h) (which recomputes the viewport), app.renderer.resize(w, h), and reapplies the new viewport to the surface sprite (scale + offset) and the render texture (size).

For an Astro embed or a sized container, ResizeObserver against the mount works the same way:

new ResizeObserver(([entry]) => {
  const { width, height } = entry!.contentRect;
  app.render.resize(width, height);
}).observe(mount);