🚀 feat: GPT-4.5, Anthropic Tool Header, and OpenAPI Ref Resolution

[danny-avila]

Summary

• Added a new 'anthropic-beta' header for Claude 3.7 to include token-efficient tools per updated documentation.
• Revised the OpenAPI $ref resolution logic to correctly resolve schema, parameter, and requestBody references, with extra test cases to verify accuracy.
• Updated GPT-4.5 handling in token calculations and vision support across API models, along with modifications in environment examples and tests.
• Refactored parser logic to extract GPT and omni model versions more reliably to support future releases.
• Improved model handling in the OpenAI client by switching to default settings and enhancing encoding logic based on model types.
• Updated the README to reflect GPT-4.5 support in the image analysis feature.
• Adjusted settings in schemas using "as const" for tighter type safety and set gpt-4o-mini as the new default for cost efficiency.

Closes #6109
Closes #6110

Checklist:

• My code adheres to this project's style guidelines
• I have performed a self-review of my own code
• I have commented in any complex areas of my code
• I have made pertinent documentation changes
• My changes do not introduce new warnings
• I have written tests demonstrating that my changes are effective or that my feature works
• Local unit tests pass with my changes
• Any changes dependent on mine have been merged and published in downstream modules