Prevent sample-answer copying from bypassing knowledge checks

[kiranfin]

User Story

As an onboarding participant, I want knowledge-check feedback to help me learn without allowing the displayed sample answer to be copied directly into an immediate retry.

Context & Motivation

During the UX test, a participant reported that after an incorrect answer, the sample answer appeared to remain visible while the question could be attempted again, making it possible to copy the sample answer instead of demonstrating understanding.

Verification Note

A code review of CheckQuestionCard.tsx, PhaseCheckModal.tsx and ReviewCheckModal.tsx on the current main did not reproduce this: the answer input is disabled for the duration that the sample answer is shown, and starting a retry clears the previous result and the sample answer together with the input, in one step. Correct/incorrect feedback there is also already distinguished by icon (CheckCircle2 / XCircle) and not by color alone.

This does not rule out the observation — it may depend on a code path, timing, or build not covered by this review. Whoever picks this up should first try to reproduce it against the exact flow and build used in the UX test before deciding whether this is still open.

Acceptance Criteria (if reproduced)

• A sample answer is never displayed next to an editable answer for the same attempt.
• Starting a retry closes or resets the previous result view.
• Server-side grading remains the source of truth.