Add structured output to ChatCompleter

[markuswustenberg]

Fixes #19

[Copilot]

Pull Request Overview

This PR adds structured output functionality to the ChatCompleter by implementing response schema support. This allows users to request JSON responses that conform to a specific structure, enabling more reliable parsing and validation of AI responses.

• Added ResponseSchema field support to ChatCompleteRequest for structured JSON outputs
• Implemented schema conversion utilities to transform Go schemas into OpenAI-compatible JSON schema format
• Added comprehensive test coverage for the structured output feature

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
chat_complete.go	Core implementation of structured output support including schema conversion and response format configuration
chat_complete_test.go	Test case demonstrating structured output functionality with JSON schema validation

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