Correct a card's prompt or answer

Write. Correct the prompt, the answer, the card coaching note, or any combination on a card this token owns. Send at least one of prompt, answer, and cardNote. cardNote null clears the card note. Coaching notes are instructions for how an agent should quiz and coach. They are not the answer, not graded content, and not the quiz prompt. A deck note applies to every card in that deck. A card note is optional and additive with the deck note. Retrieve responses (listDue, upcoming-new, inventory, getCard, reveal, and agent session start/next/grade) include deckNote and cardNote so one call carries coaching context. Scripture / dictation: The learner needs every word remembered correctly, but often answers via dictation where punctuation gets messy. They set a deck note instructing the agent to check every word exactly, but not fail on punctuation differences, and to include that reason when coaching. This is only an example — notes can be any coaching preference for how agents should quiz/coach for that deck (or a specific card). The schedule is not reset: dueAt, learning steps, ease, reps, and lapses stay. The response includes deckNote and cardNote and does not include the answer. Repeating the same text is safe and does not need an idempotency key. A retired card is 404.