We add a new `use_responsive_design` helper, for pages to opt into this
new CSS—mostly just because like… it's *worse* to apply these styles
for pages that don't expect it 😅
And then, I fix up a couple things on the item page (including in the
general items layout) to match!
I'm doing this because the species face picker layout is going to want
some responsive awareness, and I want to be doing that from the start!
Impress 2020 has had this for a while, I've wanted it for reference on
occasion, let's bring it in!
Very similar logic, and Ruby & Rails's date affordances are super
helpful for simplifying how to express it!
Oh right, I just remembered how tabs work, they join with the page when
selected! lol
Something about this still feels off to me, but idk, I find it charming
and I wanna just let it rock.
