fix: include distinct_id on $identify properties

[o-mid]

💡 Motivation and Context

Android $identify events exposed distinct_id only on the envelope, while iOS also duplicates it in properties (#272). Dashboards that key off properties.distinct_id were inconsistent across platforms.

💚 How did you test it?

• :posthog:test — PostHogTest.captures an identify event (local Gradle blocked on missing AGP 8.9.1 here; rely on CI).

📝 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

Made with Cursor

[o-mid]

CI note: Build & Test / Lint / Changeset hygiene runs are showing action_required on this fork PR (same as other external contributions). A maintainer needs to approve workflow execution on the PR before we get a real green/red signal. Wiz scans already passed.

[marandaneto]

#272 (comment)

[marandaneto]

the event already has distinct id, no need to dupe in the props map