Resolve the first/easiest intro lesson for the Test 2 lesson variant of the try_solo_activity_type_2026_05 A/B test.

Ordered by topic.display_order ASC — the same curated ordering shown to users on the /lessons listing page, so onboarding picks the same "lesson 1" a returning user would see at the top of their list. Falls back to easier levels (never harder) so we never overwhelm an A1 learner.

No auth required — anonymous onboarding visitors hit this before signing up.