Split monolithic atlas.ts into modular structure: index.ts (routing), default.ts (Claude-optimized), gpt.ts (GPT-optimized), utils.ts (shared utilities). Atlas now routes to appropriate prompt based on model type instead of overriding model settings.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>