.NET: [BREAKING] Rename session state json param

[westey (westey-m)]

Motivation and Context

Addressing review feedback: #2532

Description

• Rename parameter name for json session state to be consistent across different classes in core libraries.

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 PR renames the serializedSession parameter to serializedState in the DeserializeSessionAsync method across the codebase to achieve consistent naming. This is a breaking API change that addresses review feedback from PR #2532.

Changes:

• Renamed parameter from serializedSession to serializedState in DeserializeSessionAsync method signatures across all AIAgent implementations
• Updated XML documentation comments to reflect the parameter rename
• Updated parameter usage within method bodies and session constructors

Reviewed changes

Copilot reviewed 32 out of 32 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
dotnet/src/Microsoft.Agents.AI.Abstractions/AIAgent.cs	Updated abstract method signature and XML docs for DeserializeSessionAsync
dotnet/src/Microsoft.Agents.AI.Abstractions/DelegatingAIAgent.cs	Updated DeserializeSessionAsync implementation to use new parameter name
dotnet/src/Microsoft.Agents.AI.Abstractions/InMemoryAgentSession.cs	Updated constructor parameter name and XML docs
dotnet/src/Microsoft.Agents.AI.Abstractions/ServiceIdAgentSession.cs	Updated constructor parameter name and XML docs
dotnet/src/Microsoft.Agents.AI.A2A/A2AAgent.cs	Updated DeserializeSessionAsync implementation
dotnet/src/Microsoft.Agents.AI.CopilotStudio/CopilotStudioAgent.cs	Updated DeserializeSessionAsync implementation
dotnet/src/Microsoft.Agents.AI.DurableTask/DurableAIAgent.cs	Updated DeserializeSessionAsync implementation and XML docs
dotnet/src/Microsoft.Agents.AI.DurableTask/DurableAIAgentProxy.cs	Updated DeserializeSessionAsync implementation
dotnet/src/Microsoft.Agents.AI.GitHub.Copilot/GitHubCopilotAgent.cs	Updated DeserializeSessionAsync implementation
dotnet/src/Microsoft.Agents.AI.Purview/PurviewAgent.cs	Updated DeserializeSessionAsync implementation
dotnet/src/Microsoft.Agents.AI.Workflows/WorkflowHostAgent.cs	Updated DeserializeSessionAsync implementation
dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs	Updated DeserializeSessionAsync implementation
dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgentSession.cs	Updated DeserializeAsync internal method parameter name and XML docs
dotnet/samples/GettingStarted/AgentProviders/Agent_With_CustomImplementation/Program.cs	Updated DeserializeSessionAsync implementation in sample
dotnet/tests/* (18 test files)	Updated DeserializeSessionAsync implementations in test agents