The Timeline doesn't change the active post at the correct scroll height on iOS when the URL bar is expanded

[camdendotlol]

1. Visit https://unitedfruitcompany.vercel.app/timeline on an iPhone using Safari.
2. Scroll down several items.
3. Scroll up a little bit to expand the URL bar.
4. The detection of which post is active is skewed, so the test labels appear directly in the middle of the screen instead of fading in on entry.
5. The calculation gets more skewed the farther down the screen you go.

4cc9cf5 helps with this issue by using screen.height on iOS devices, and might be tolerable as a permanent fix if time is short. I will see how bad it gets once more Timeline posts are added.

[camdendotlol]

Got it working satisfactorily on iOS with 646f0bf but it's still goofy on Android devices.