This is a nice extra error handler to have, but note that it *won't*
catch the case where the iframe successfully loads but the page returns
a bad status code. In this case, we'll just show the loading state
forever.
The most notable thing here is that we keep the movie iframes running!
So if you're trying different pets for an animated item, the animation
keeps going while the new pet layers load alongside it.
This is also nice for like, the species/color picker form, so we're not
taking away input elements from people who depend on e.g. keyboard
focus.
Oh right okay, attributes like `status="loading"` are more of an API
for the caller, whereas the internal state API is where you wanna put
things that are meant to be used in CSS selectors and stuff.
Instead of doing all this listening to Turbo events etc to know when
outfit layers might have changed, making it a custom element and wiring
in the behavior to its actual lifecycle makes it always Just Work!
