Unnecessary DOM updates

In the [_Editorial Engine_ demo](https://chenglou.me/pretext/editorial-engine), huge chunks of the DOM are updated at every tick, even elements that didn't need to change.

https://github.com/user-attachments/assets/0809d137-e587-4e2a-85e7-c172c56bea87

Notice how the line that says "THE FUTURE" is not changing, yet its DOM element is beign replaced all the time.

This may (or may not) be related to #151

Start with the Editorial Engine demo and investigate why unchanged DOM elements, such as the line reading “THE FUTURE,” are replaced on every tick. Read the related issue #151 for context and use the demo behavior as the check. Done means unchanged elements are no longer unnecessarily replaced while the demo still updates correctly.

Written by the indexing model from the issue text.