[fix] reset scroll when navigated from scrolled page

[bluwy]

Fixes #2733 and maybe #2664

Move the scroll to top logic before the new route mounts so that we can properly compare the pageYOffset === 0. This works because scroll position is preserved between route changes by default.

I also updated our isVisble() tests to is_intersecting_viewport(), since isVisble checks for visibility anywhere in the document. is_intersecting_viewport makes sure they are in the viewport.

Nonetheless, @mquandalle and @mikenikles I'd appreciate if y'all can try to see if this branch fixes your issue as well.

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[benmccann]

Could this result in a behavior of jumping to the top of the page and the down to the final scroll position?

[bluwy]

Could this result in a behavior of jumping to the top of the page and the down to the final scroll position?

This would technically happen from the code flow, but it happens between an await 0 so it should be fast enough that it's not noticeable, but otherwise I don't see another way around this unfortunately, unless we can hook into an event loop where the component is mounted but not yet called onMount().

[benmccann]

thanks for updating these tests!