Platform-derived answer envelope (from questionnaire.yaml).
`json
{
"instrument": {"id": "price_sensitivity_v1", "title": "Price Sensitivity Survey — Hasbro Gaming Candy Land Kingdom"},
"answers": [
{
"questionId": "q_price_matters",
"value": "`
Use exact questionId values from the questionnaire.
For choice questions, value must be the exact choice id (or list of ids for multi-select).
Default surveys emit questionId + value only (choice / likert / bool).