.NET: Update to M.E.AI 10.3.0

[stephentoub]

No description provided.

[Copilot]

Pull request overview

This pull request updates the Microsoft.Extensions.AI package family to version 10.3.0, along with related System.* packages (10.0.2 → 10.0.3) and adopts new APIs introduced in this version.

Changes:

• Updated M.E.AI packages from 10.2.0 to 10.3.0 and System.* packages from 10.0.2 to 10.0.3
• Adopted new ChatOptions.Reasoning API to replace the previous RawRepresentationFactory approach for configuring reasoning models
• Added support for FunctionCallContent.InformationalOnly flag to skip invocation of informational-only function calls
• Refactored DataContent handling to use new LoadFromAsync() and SaveToAsync() helper methods
• Improved temp directory cleanup in GitHubCopilotAgent by creating and deleting a single directory instead of tracking individual files

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
dotnet/Directory.Packages.props	Package version updates for M.E.AI (10.2.0→10.3.0) and System.* libraries (10.0.2→10.0.3)
dotnet/src/Microsoft.Agents.AI.AzureAI/AzureAIProjectChatClientExtensions.cs	Added ToResponseReasoningOptions mapper and updated CreateAIAgentAsync to use ChatOptions.Reasoning
dotnet/src/Microsoft.Agents.AI.GitHub.Copilot/GitHubCopilotAgent.cs	Refactored to use DataContent.SaveToAsync() and improved temp directory cleanup
dotnet/src/Shared/Workflows/Execution/WorkflowRunner.cs	Added check for FunctionCallContent.InformationalOnly flag before invocation
dotnet/samples/GettingStarted/AgentWithOpenAI/Agent_OpenAI_Step02_Reasoning/Program.cs	Updated to use new ChatOptions.Reasoning API instead of RawRepresentationFactory
dotnet/samples/GettingStarted/FoundryAgents/FoundryAgents_Step10_UsingImages/Program.cs	Updated to use DataContent.LoadFromAsync() instead of manual file reading
dotnet/tests/Microsoft.Agents.AI.UnitTests/FunctionInvocationDelegatingAgentTests.cs	Refactored mock setup (though using helper method would be more consistent)