feat(surveys): add optional intro screen before the first question

[jakesciotto]

💡 Motivation and Context

Surveys can show a confirmation ("thank you") screen after the last question, but there is no equivalent screen before the first one.

This is the posthog-android part of the cross-SDK intro screen rollout tracked in PostHog/posthog#74064. The web/RN renderer shipped in PostHog/posthog-js#4436; this PR brings the Android model layer and the Compose UI module to parity.

What it does:

• New SurveyAppearance fields (appended last so existing positional copy()/componentN() usages keep their meaning): displayIntroScreen, introScreenHeader, introScreenDescription, introScreenDescriptionContentType, introScreenButtonText. Mapped onto PostHogDisplaySurveyAppearance for custom delegates.
• New IntroScreen composable in posthog-android-surveys-compose, the leading mirror of ConfirmationScreen, shown by SurveySheet before the first question when displayIntroScreen is on. The description follows the module's existing TEXT-only rendering rule (HTML stays a known gap).
• Advancing past the intro flips local sheet state only: no onSubmit call, no response recorded, no survey event. The X button keeps dismissing the whole survey with the normal survey dismissed event, and the confirmation branch still wins for completed surveys.
• Intro copy is translatable (introScreenHeader / introScreenDescription / introScreenButtonText), wired through SurveyTranslation, the translation applier's change gate, and the display mapping.
• For custom (non-Compose) delegates, reading the new fields off survey.appearance is all that's needed; no delegate interface changes.

💚 How did you test it?

Unit tests added/extended:

• SurveyAppearanceMappingTest: intro fields map onto the display appearance; missing fields default to disabled.
• SurveyTranslationsTest: JSON fixture now carries intro fields; translated header/button apply with untranslated description falling back, and the untranslated path renders originals.

Written on Linux without a JVM/Android SDK, so Gradle did not run locally — please rely on CI (make compile). ⚠️ posthog/api/posthog.api was updated by hand following the binary-compatibility-validator format; if apiCheck disagrees, make api will produce the canonical dump.

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed.
• No breaking change or entry added to the changelog.

If releasing new changes

• Ran pnpm changeset to generate a changeset file (.changeset/survey-intro-screen.md, minor for posthog + posthog-android-surveys-compose)

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

• Authored with PostHog Code (Claude) as part of the cross-SDK rollout requested in review of feat(surveys): add optional intro screen shown before the first question posthog-js#4436; design per Feature request: Survey intro/start screen (shown before the first question) posthog#74064.
• Key decisions: intro state is a rememberSaveable flag inside SurveySheet (survives configuration changes, never touches onSubmit/onClose), and the new data-class fields were deliberately appended after the existing ones with defaults to avoid shifting componentN/copy positions.

---

Created with PostHog Code

[greptile-apps]

Prompt To Fix All With AI

### Issue 1
posthog/src/main/java/com/posthog/internal/surveys/SurveyTranslationApplier.kt:80-90
**Disabled intro sets survey language**

When `displayIntroScreen` is false or omitted but its translation contains different intro copy, these checks still set `matchedKey`, causing survey events to include `$survey_language` even though none of that translated content was displayed.

```suggestion
    if (appearance?.displayIntroScreen == true) {
        if (translation.introScreenHeader != null && translation.introScreenHeader != appearance.introScreenHeader) return true
        if (translation.introScreenDescription != null &&
            translation.introScreenDescription != appearance.introScreenDescription
        ) {
            return true
        }
        if (translation.introScreenButtonText != null &&
            translation.introScreenButtonText != appearance.introScreenButtonText
        ) {
            return true
        }
    }
```

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

_{Reviews (1): Last reviewed commit: "feat(surveys): add optional intro screen..." | Re-trigger Greptile}

[github-actions]

posthog-android Compliance Report

Date: 2026-08-06 22:57:02 UTC
Duration: 118390ms

✅ All Tests Passed!

46/46 tests passed

---

Capture Tests

✅ 29/29 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	392ms
Format Validation.Event Has Uuid	✅	27ms
Format Validation.Event Has Lib Properties	✅	28ms
Format Validation.Distinct Id Is String	✅	30ms
Format Validation.Token Is Present	✅	25ms
Format Validation.Custom Properties Preserved	✅	27ms
Format Validation.Event Has Timestamp	✅	30ms
Retry Behavior.Retries On 503	✅	7025ms
Retry Behavior.Does Not Retry On 400	✅	4023ms
Retry Behavior.Does Not Retry On 401	✅	4026ms
Retry Behavior.Respects Retry After Header	✅	7028ms
Retry Behavior.Implements Backoff	✅	17030ms
Retry Behavior.Retries On 500	✅	7016ms
Retry Behavior.Retries On 502	✅	7019ms
Retry Behavior.Retries On 504	✅	7020ms
Retry Behavior.Max Retries Respected	✅	17034ms
Deduplication.Generates Unique Uuids	✅	37ms
Deduplication.Preserves Uuid On Retry	✅	7012ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	12030ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	7018ms
Deduplication.No Duplicate Events In Batch	✅	36ms
Deduplication.Different Events Have Different Uuids	✅	21ms
Compression.Sends Gzip When Enabled	✅	19ms
Batch Format.Uses Proper Batch Structure	✅	18ms
Batch Format.Flush With No Events Sends Nothing	✅	11ms
Batch Format.Multiple Events Batched Together	✅	32ms
Error Handling.Does Not Retry On 403	✅	4020ms
Error Handling.Does Not Retry On 413	✅	4021ms
Error Handling.Retries On 408	✅	5028ms

Feature_Flags Tests

✅ 17/17 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	32ms
Request Payload.Flags Request Uses V2 Query Param	✅	22ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	19ms
Request Payload.Flags Request Omits Authorization Header	✅	26ms
Request Payload.Token In Flags Body Matches Init	✅	32ms
Request Payload.Groups Round Trip	✅	20ms
Request Payload.Groups Default To Empty Object	✅	24ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	20ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	20ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	21ms
Request Lifecycle.No Flags Request On Init Alone	✅	9ms
Request Lifecycle.No Flags Request On Normal Capture	✅	22ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	37ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	18ms
Retry Behavior.Retries Flags On 502	✅	323ms
Retry Behavior.Retries Flags On 504	✅	324ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	21ms