Analyzes CircleCI configuration files (config.yml) and provides optimization recommendations based on best practices. Use when (1) User mentions 'optimize config.yml', 'improve CircleCI setup', or 'review CircleCI configuration', (2) User wants to reduce build costs, execution time, or credit consumption, (3) User asks about resource_class settings, caching strategies, parallelization, or Docker Layer Caching, (4) User mentions CircleCI performance issues like 'builds are slow' or 'tests take too long', (5) User requests best practices check or wants to identify anti-patterns. Performs static analysis of resource_class optimization, cache strategy evaluation, parallelization opportunities, Docker Layer Caching configuration, Orbs utilization, workflow structure, and general best practices. DO NOT use for other CI/CD tools (GitHub Actions, Jenkins, GitLab CI), Dockerfile optimization, CircleCI account management, or Orbs development.