Pressing space bar on Firefox mobile changes previous word

On Android, when trying the editor in Firefox mobile, after a new carriage return, writing a word and pressing space bar, the cursor moves back and changes the word in a weird pattern.

##### Steps to Reproduce

1. On **Android phone**, go to https://trix-editor.org/
2. go to the bottom of the page and put cursor at last character
3. insert 3 CR to create a bunch of empty lines
4. type a word and then the space bar
5. the word will be changed

See recording

https://github.com/basecamp/trix/assets/1375981/78a5cb04-951b-4723-a3ba-9163305470c6

##### Details

* Trix version: https://trix-editor.org/
* Browser name and version: Firefox 121
* Operating system: Android 9

Reproduce the issue at https://trix-editor.org/ on an Android phone running Firefox 121 by adding three carriage returns, typing a word, and pressing space. Trace the editor behavior around the resulting cursor movement and word change; done means the word and cursor remain correct after pressing space.

Written by the indexing model from the issue text.