Retrying an image at a variant that exists

Some sources publish several renditions of the same picture under predictable URLs, and only some of them are guaranteed. Point at the high-resolution one and a minority of records answer with a 404. The image itself degrades gracefully — a placeholder appears. Everything derived from the image does not.

// adapted — the URL is composition state, keyed on the record, and both the request and its
// cache key read that same state
var imageUrl by remember(record.id) { mutableStateOf(record.imageUrl) }