Fetches one PNG, JPEG, or WebP image from a Kalpana URL (a template or asset previewUrl, or a downloadUrl from get_batch_outputs) and returns it as image content with its content type and byte size. Other hosts, other file types, and files over 5 MB are rejected, and a fetch gives up after 15 seconds. It shows one image per call; it does not build contact sheets or render templates, whose look comes from their previewUrl.