This is the float you would nest under, so from a child's perspective it is
the "parent". A component that owns a float (via useFloatStack) gets
its own reference from that hook; useFloat returns the one above it.
Use this in any component that needs the enclosing float without owning one —
e.g. a menu item calling closeChild() on hover to dismiss an open sibling
submenu. Such components are not reached by props, only by context.
Returns the FloatReference of the enclosing region (i.e. the float this component is rendered inside), or
nullwhen there is no ancestor float.