.NET: [BREAKING] Provide agent and session to AIContextProvider & ChatHistoryProvider

[westey (westey-m)]

Motivation and Context

It's valuable for an AIContextProvider or ChatHistoryProvider to know which agent or session it is working with. This allows greater flexibility for implementers to modify the behavior of the providers based on the current session state or agent details.

This also paves the way for a key scenario where state for a provider should ideally be contributed to the session, making providers stateless and reusable. A PR addressing this to follow.

Description

• Pass Agent and AgentSession to AIContextProvider or ChatHistoryProvider

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.

[Copilot]

Pull request overview

This pull request enhances the AIContextProvider and ChatHistoryProvider abstractions by passing the AIAgent and AgentSession to their context objects. This enables providers to access session state and agent details, supporting more flexible and stateless provider implementations.

Changes:

• Updated AIContextProvider.InvokingContext and AIContextProvider.InvokedContext to accept and store AIAgent and AgentSession? parameters
• Updated ChatHistoryProvider.InvokingContext and ChatHistoryProvider.InvokedContext to accept and store AIAgent and AgentSession? parameters
• Modified ChatClientAgent to pass this (agent) and session to all provider context instantiations
• Updated all test files, integration tests, and samples to use the new constructor signatures with mock agents/sessions

Reviewed changes

Copilot reviewed 26 out of 26 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
dotnet/src/Microsoft.Agents.AI.Abstractions/AIContextProvider.cs	Added Agent and Session properties to InvokingContext and InvokedContext with null validation for agent
dotnet/src/Microsoft.Agents.AI.Abstractions/ChatHistoryProvider.cs	Added Agent and Session properties to InvokingContext and InvokedContext with null validation for agent
dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs	Updated all provider context instantiations to pass this and session; changed notification methods from static to instance methods
dotnet/samples/GettingStarted/AgentProviders/Agent_With_CustomImplementation/Program.cs	Updated custom agent implementation to use new context constructor signatures
dotnet/tests/Microsoft.Agents.AI.UnitTests/TestJsonSerializerContext.cs	Added JSON serialization support for test Animal class
dotnet/tests/Microsoft.Agents.AI.UnitTests/ChatClient/ChatClientAgentSessionTests.cs	Added internal Animal class for testing
dotnet/tests/.UnitTests/.cs	Added mock agent/session fields and updated all context instantiations
dotnet/tests/.IntegrationTests/.cs	Updated test fixtures to accept agent parameter in GetChatHistoryAsync method
dotnet/tests/AgentConformance.IntegrationTests/IAgentFixture.cs	Updated interface signature for GetChatHistoryAsync to include agent parameter