[dialog] Lock scroll on iOS if navbar is collapsed #1893
Description
In #1890 the scroll lock for iOS was changed to a basic technique (overflow: hidden on <html>) that only works if the navbar is expanded.
Numerous bugs and issues arise on iOS when trying to robustly lock the scroll. A solution must avoid all of these bugs to be implemented:
- Textboxes must slide into view when focused, nor cause a glitchy scroll animation
- The navbar must not force itself into view and cause layout shift
- Scroll containers must not flicker upon closing a popup when it has an exit animation