improve visual display of sunburst w a large number of top tier children

right now if there are a lot of top tier children, the list of children to the right of the sunburst gets to be VERY tall and the sunburst shifts so far down its out of view. at first i thought it failed to render for some reason. the list should probably scroll independently of the rest of the page, and the sunburst should always be at top.

'Leptospira' would be a good example of this once #550 is merged

Reproduce the layout problem with a sunburst having many top-tier children, using “Leptospira” as the example once #550 is merged. Find the sunburst and adjacent child-list entry points, then verify that the sunburst remains at the top while the child list scrolls independently and no longer pushes it out of view.

Written by the indexing model from the issue text.