Editor does not reset history when changing questions

**Describe the bug**
When changing questions, the editor's history does not get reset, meaning that if one undoes after changing questions, it will reset to previous solution

**To Reproduce**
Steps to reproduce the behavior:
1. Open competitor UI
2. Type in a solution
3. Change questions
4. Press Ctrl-Z or whatever 'undo' is in your keybinds

**Expected behavior**
Undo here should do nothing

Start in the competitor UI and reproduce the issue by typing a solution, changing questions, and pressing Ctrl-Z. Trace the editor history handling around question changes, then verify that changing questions clears the prior history and undo no longer restores the previous solution.

Written by the indexing model from the issue text.