Passed to useAnchoredFloat by the component that owns the panel, in pixels. The heights let the hook size the panel's scrolling part to the room left.
width: number | "anchor"
A width, or "anchor" for the anchor's own. Either shrinks to fit a narrower viewport.
chromeHeight: number
The height of the panel's parts that don't scroll, borders included.
minContentHeight: number
maxContentHeight: number