Use this skill to statically review whether a type-level abstraction in shared or published TypeScript code actually proves what its signature claims: generic variance, conditional and mapped type correctness, dishonest type predicates, unsound narrowing, `satisfies` versus annotation, branded/nominal modelling, and `unknown`-first discipline. Reads source and sanitized `tsconfig.json` only; it never reviews a frontend application diff and never compiles or runs code.
