SplitContentLayout doesn't resize when page layout changes

[a-type]

This seems like a hard problem to solve.

If the size of the header changes (or external layout in general changes), SplitContentLayout doesn't change with it.

May require some MutationObservers? Or a clever solution with IntersectionObserver? Or just good old fashioned polling? Or a way to pass in an event emitter which triggers a recalculation that the user would then have to manually trigger events on for page changes?