fix: Render extreme aspect ratios instead of raising

[elektronaut]

ImageSizing#fit has raised InvalidSizeOptions since #142 when a fitted size lands under a pixel, which the view helpers reach for an image far enough from square. dynamic_picture_tag goes sub-pixel at its smallest breakpoints past roughly 350:1, and dynamic_image_tag raises past the width it is asked for — size: "1200x" past 1200:1, a 50 pixel thumbnail past 50:1. Neither image rendered before #142 either, but the failure moved from one broken img to a raise in the view, so a single uploaded image takes down every page that renders it.

ImageSizing#fit_renderable returns the smallest size the image can be rendered at, the whole frame scaled until its short side is one pixel, rather than raising. dynamic_image_tag and dynamic_image_url render at that size, and the tag lays the image out at the size that was asked for, so a 2000x1 image asked for "1200x" renders 2000x1 and reports a width of 1200 and a height of 1. Growing the size keeps the image's own aspect, so the frame is never cropped, and the file is never larger than the stored image: 352 bytes for a 1000x2 WebP.

Picture drops the candidate widths it can't render instead, since a srcset descriptor has to match the width of the file behind it. An image too extreme for any breakpoint gets a single candidate at its own width.

Requesting a size with crop: true still raises when the crop leaves less than a pixel, as does Model::Transformations#resize.