Think like a product manager before changing React Doctor's public surface — CLI commands/flags, the 0–100 score, config (doctor.config.*), the JSON report schema, package APIs (inspect()/diagnose()), the GitHub Action, the website, and the canonical prompts. A step-by-step runbook for a user-facing change — locate the surface, search for a reuse candidate, wire one telemetry metric, add the compatibility artifacts (changeset / schemaVersion / action tag), update docs, and record a kill metric. Not for lint rules, which have their own pipeline. Also runs when the user types `/product-thinking`.