Add annotations to chat stream result

[batanus]

What

Add Annotations property to ChatStreamResult object

Why

When OpenAI uses web tool call in stream mode - it returns annotation object for ChatStreamResult as well

Affected Areas

ChatStreamResult, Annotation structs

[Copilot]

Pull request overview

This PR adds support for annotations in chat stream results, enabling the handling of web search tool citations in streaming mode. The Annotation struct is extracted into a shared model and added to ChatStreamResult.

Key Changes:

• Extracted Annotation struct from ChatResult.Choice into a standalone public model
• Added annotations property to ChatStreamResult.Choice.Delta

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
Sources/OpenAI/Public/Models/ChatStreamResult.swift	Added annotations field to Delta struct with documentation referencing web search tool
Sources/OpenAI/Public/Models/ChatResult.swift	Removed nested Annotation struct from Choice
Sources/OpenAI/Public/Models/Annotation.swift	Created new file with extracted Annotation struct, updated access modifiers to public

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[Copilot]

The documentation comment spans multiple lines unnecessarily. Consider consolidating into a single-line comment or using a more concise format that doesn't require a URL on a separate line.

Suggested change

	/// Annotations for the message, when applicable, as when using the web search tool.
	/// Web search tool: https://platform.openai.com/docs/guides/tools-web-search?api-mode=chat
	/// Annotations for the message, when applicable, as when using the web search tool: https://platform.openai.com/docs/guides/tools-web-search?api-mode=chat