Hide answer feedback until after submission

[sfw]

Summary

• Frontend: Option body text (containing explanations and correctness hints like "Correct!") was displayed alongside each choice before the learner submitted, giving away the answer. Now option.body is hidden until after submission, with correct/incorrect visual styling (green checkmark / red X) applied post-submit. Options are also disabled after submission to prevent changes.
• Backend prompt: Updated both batch and streaming schema contracts to explicitly instruct the LLM that option body must never reveal whether an option is correct or incorrect — body should describe the reasoning or misconception behind the choice, not its correctness.

Test plan

• Backend tests: 721 passed
• Frontend tests: 289 passed
• Backend lint clean
• Frontend lint clean
• Frontend production build passes
• Manual: verify option body text is hidden before submission
• Manual: verify correct option shows green styling and incorrect shows red after submit
• Manual: verify options are disabled after submission

🤖 Generated with Claude Code