Portal.view.home => non-snapped scrolling allows to scroll the document outside of the visible area

this one is super weird:

i have not found the root-cause, since i never encountered it for any neo app before.

the only way to fix it was adding position: fixed to the viewport div. we need to limit it to direct viewport children of the document body to not break LivePreviews (which can mount a viewport into a div).

@rwaters