Getting these in puts us in a spot where we can pretty easily see the
differences between uplot and recharts.

This is just a touch more portable.

Verbose, but fairly straightforward. The only meaningful changes you
should see are the lack of a top grid line (since uplot does tick
calculation, this would often be quite tight with the line below) and
uplot's tick selection logic replacing ours (which is for the greater
good).

Any canvas drawing element is going to need themes this way. I
considered doing something more involved, like computing the style
within the subscription, or actually making a the subscription an effect
hook, but the thing is, you kind of want to only use getComputedStyle
consciously.

If you passed an anonymous function as the yAxisTickFormatter, that
would cause rerender cycles that screwed with hovering, because the
graph was being constantly re-created. You could say the caller is just
responsible for not doing that, but I was feeling generous.

This reverts commit 9e153db.

This also makes some design decisions unilaterally, such as a rotating
color palette, and legends/what they look like.

I'm not entirely sure this is what we're going to love. As you drag the
mouse around, the alpha changes are quite noisy. I wonder if we can get
by with just highlighting the active point (instead of _all_ the points
on that X) and stick the color itself in the tooltip?

The other thought I'm having here: in the legend, there's not much to do
other than throw all the legend values in line like that (or come up
with aliases, but then you need some sort of hover). Within a tooltip,
though, this could be actually formatted!

Maybe we'll actually hang on to something like this in the long run, but
for now it's just plain handy.

I don't think there's a reasonable way to use the design system for this
directly at the moment!