Turn a rough feature idea into a paste-ready Lovable prompt — goal, screens, data, states, edge cases, and an explicit do-not-touch list. Use when the user says "write a Lovable prompt", "brief for this feature", "tell Lovable to build", "spec this screen", or is about to paste vague instructions into an AI app builder. Don't use for writing the database migration behind the feature — use supabase-migration-writer.
