Diagnose and fix CI/CD failures related to Lint errors and test failures. Use when: (1) User mentions CI/CD failures, lint errors, or test failures, (2) User asks to fix code quality issues or make tests pass, (3) User requests to check or verify code before committing/pushing, (4) Working on a task that requires running lint or tests to validate changes. This skill provides systematic workflows for identifying, diagnosing, and fixing common Lint and test errors in TypeScript/React projects using ESLint, Prettier, and Vitest.