Agent Skills: typescript

JavaScript/TypeScript language engineering — the strictest-profile type system (discriminated unions, branded types, satisfies), parse-don't-validate boundaries with Zod, ESM and the Node runtime, typescript-eslint discipline (no floating promises), and Vitest/MSW/fast-check testing. Load whenever writing, editing, or reviewing .ts/.tsx/.js/.mjs code, tsconfig or package.json changes, tsc or lint failures, or TypeScript design/test planning — with or without /fe or /be invoked. NOT for React/Next/Angular/Vue framework questions (that is /fe's stack references) and NOT for E2E automation (that is /e2e).