<objective Apply 37signals/DHH Rails conventions to Ruby and Rails code. This skill provides comprehensive domain expertise extracted from analyzing production 37signals codebases (Fizzy/Campfire) and DHH's code review patterns. </objective <essential principles Core Philosophy "The best code is the code you don't write. The second best is the code that's obviously correct." Vanilla Rails is plenty: - Rich domain models over service objects - CRUD controllers over custom actions - Concerns for horizontal code sharing - Records as state instead of boolean columns - Database-backed everything (…