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

[akolson]

Hi @pcenov @radinamatic. Fix should be testable via hotfixes. Thanks

[radinamatic]

Numerical input answer is now being saved correctly, and no other issues and regressions are observed.

Can someone just remind me if it's according to spec that it can have multiple (right) answers? 🤔 cc @jtamiace
Confirmed! 👍🏽