Add a Reset/Restart Option for Course Challenges and Unit Tests

Khan Academy's mastery system is a great way to encourage learning, but I think it would benefit from a reset/restart option for course challenges and unit tests.

Right now, a single accidental misclick or unintended answer can lower your proficiency level, even if it doesn't reflect your actual understanding of the material. This is especially frustrating for learners who are aiming for full mastery or simply want to retake a challenge from the beginning.

Adding an option to restart a challenge would give learners more control over their progress without changing the platform's learning goals. Whether someone wants to recover from an accidental click, restart after an interruption, or measure their understanding with a fresh attempt, this feature would make the mastery system feel more accurate and user-friendly.

Since Khan Academy is designed to support self-paced learning, giving users the ability to reset or restart a challenge would be a valuable quality-of-life improvement.