Agent Skills: fa-product-soft-launch

Provides the Stage-8 build-iteration and soft-launch playbook for consumer one-off / in-app-purchase products - always-green trunk with feature-flags, a versioned telemetry/event taxonomy wired before external testers, closed/open beta hardening, soft-launch in cheap representative geos with attribution, reading D1/D7/D30 + conversion + ARPPU/ARPDAU by cohort/source, modeling pLTV vs CPI, one-variable A/B tuning, iterate-or-kill discipline, and clearing the multi-condition scale gate. Use to prove real-money retention before paid scale. Money-gated and net-of-fee aware (require net LTV > CPI + payback).