Surveys: Support shuffle questions and shuffle options

🚨 IMPORTANT

This issue is likely user-facing in the main PostHog app, see surveyVersionRequirements.ts. If you delete or close this issue, be sure to update the version requirements list here.

Summary

The posthog-flutter SDK does not support two shuffle features for surveys in its built-in rendering:

1. Shuffle Questions (shuffleQuestions)

SurveyBottomSheet._buildQuestion() iterates through survey.questions[_currentIndex] in order. The shuffleQuestions field is not present anywhere in the Flutter SDK codebase. The underlying native SDKs parse the field but don't expose it in their display models.

2. Shuffle Options (shuffleOptions)

The shuffleOptions boolean IS available on PostHogDisplayChoiceQuestion, but the built-in SurveyBottomSheet passes choiceQuestion.choices directly to ChoiceQuestionWidget without checking shuffleOptions or shuffling the choices. ChoiceQuestionWidget renders widget.choices in original order.

Expected Behavior

• When survey.appearance.shuffleQuestions is true, questions should be presented in a randomized order (unless enable_partial_responses is true)
• When question.shuffleOptions is true on a choice question, choices should be randomized (keeping the open-ended choice at end if present)

Reference Implementation

See posthog-js browser: packages/browser/src/extensions/surveys/surveys-extension-utils.tsx

• getDisplayOrderQuestions() for question shuffling
• getDisplayOrderChoices() for option shuffling

Tracking

This is tracked in the survey SDK feature parity issue: https://github.com/PostHog/posthog/issues/45658

This issue was generated by Claude using the /survey-sdk-audit skill.

Start with SurveyBottomSheet._buildQuestion() and ChoiceQuestionWidget, then compare their behavior with getDisplayOrderQuestions() and getDisplayOrderChoices() in packages/browser/src/extensions/surveys/surveys-extension-utils.tsx. Check surveyVersionRequirements.ts before making changes. Done means questions and choices are randomized under the stated conditions, with an open-ended choice remaining last.