Fix cost estimation with accurate pricing and improve error handling

- Fix cost calculation to use correct per-token rates (input/output separate)
- Update Claude 3.7 Sonnet: /MTok input, /MTok output
- Update OpenAI models with latest GPT-4.1, GPT-4o pricing
- Add separate input/output cost functions for accurate estimation
- Fix guidelines path resolution for global installations
- Add repomix optimization with --remove-comments --remove-empty-lines
- Improve text sanitization for endoftext token issues
- All linting tests now pass

Author: rainmana