Instead of hand-rolling HTML, this offers helpers like `f.field`, to
help ensure the HTML is consistent, and to keep the templates more
focused on the unique form elements.
Most notable change here is extracting the pose option bubbles into a
`data-type="radio-grid"`, and pulling that into the `.support-form`
CSS. My rationale is that, unlike most fields, this field benefits from
being 100%-width, and I don't want to specify that as an override if I
can avoid it, because that's fragile-y.
Instead, I extract this into a generic type of field that
`.support-form` can use (it feels pretty reusable anyway!), and require
the caller to specify how many columns they want as `--num-columns`.
Specifically, I'm going for a more-vertical layout, cuz I want to bring
PetState over to it, and the weird grid situation wasn't gonna fit the
big pose label radios.
