Onboarding that ends when users actually activate.

Welcome series triggered by signed_up_at, branching on user actions, terminating the moment activated_at is set. Real activation, not opens or clicks.

• Trigger: signed_up_at filled
• Channel: Email welcome series, optional WhatsApp
• Goal: activated_at not null (your definition of activation)
• Variations: vibe-coder onboarding, B2B onboarding, freemium onboarding