[WIP] Add ToolChoice for message requests

[gembancud]

[WIP] Implement ToolChoice for Messages API

Status

• Initial implementation of ToolChoice enum and integration with MessagesRequestBody
• Not yet ready for merge - opened for visibility and early feedback
• Testing, documentation, and further integration pending

Next Steps

• Complete testing
• Update documentation
• Ensure compatibility with existing features

Feedback Request

• Any initial thoughts on the approach?
• Specific areas to focus on or considerations to keep in mind?

It would be ideal to enforce tool use. Similarly, helper functions have been added to simple extract tool info as a proxy for JSON data extraction without having to write out proc macros