.NET: Support primitives and arrays for SO

[SergeyMenshykh]

Motivation and Context

The new solution for structured output is not handling primitives and arrays, which means that LLMs will reject requests where the SO schema does not have an object as the root.

Description

• Wrap primitives, arrays, and enums provided as SO types into a JSON object schema.
• Unwrap the response from the agent if it was wrapped.

[Copilot]

Pull request overview

This PR adds support for primitives, arrays, and enums in structured output by automatically wrapping non-object JSON schemas. Previously, the structured output feature only supported object types at the root level, which caused LLMs to reject requests for primitive or array types.

Changes:

• Wraps primitives, arrays, and enums in a JSON object schema with a "data" property when used as structured output types
• Unwraps the response from the agent when deserializing wrapped types
• Adds comprehensive unit tests and an integration test for primitive and array type handling

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
dotnet/src/Microsoft.Agents.AI.Abstractions/AIAgentStructuredOutput.cs	Implements schema wrapping logic with EnsureObjectSchema, SchemaRepresentsObject, and helper methods to wrap non-object schemas
dotnet/src/Microsoft.Agents.AI.Abstractions/AgentResponse{T}.cs	Adds IsWrappedInObject property and UnwrapDataProperty method to unwrap responses from wrapped schemas
dotnet/tests/Microsoft.Agents.AI.Abstractions.UnitTests/AIAgentStructuredOutputTests.cs	Adds unit tests for schema wrapping, response unwrapping, and end-to-end scenarios
dotnet/tests/AgentConformance.IntegrationTests/StructuredOutputRunTests.cs	Adds integration test for primitive type structured output

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.