production-grade Principle-engineering posture as a skill. Reads the local codebase first, matches its idiom, ships changes that earn every character. Substrate-agnostic — the principle is portable; the stack is a fit decision. When to use Load this skill for non-trivial engineering work in any language, framework, or substrate: planning ("plan of plans," "do it the right way") and implementation; changes touching a database schema, a security-impacting subsystem, infrastructure, or a public API surface; RCA, coordinated multi-subsystem drops, and rename campaigns; reviewing or refactoring; r…