Save numerical input answers

[akolson]

Summary

This pr fixes a bug where a numeric input answer is not saved and question is marked as incomplete after closing the exercise editor.

Before

num-input.mp4

After

Screen.Recording.2025-03-11.at.08.42.30.mov

References

Fixes#4910

Reviewer guidance

1. Select Numeric input type of question in the exercise editor.
2. Add 1 answer and close the editor.
3. Reopen the exercise and ensure the ❗ mark indicating the incomplete question is not displayed
4. Try different variations as illustrated in the before video to check if the issue can be replicated

[rtibbles]

Not seeing any issues in my testing, and I think whatever extra caution we initially had that added this catch in the first place is no longer required.

One thing is that we should rebase this on top of hotfixes rather than unstable and target the PR there, so we can release it as a patch.

[akolson]

New pr pointing to hotfixes. Closing this cc @rtibbles