Complete .NET agent/harness port

[michelle-clayton-work]

Complete the agent/harness port from .NET for non-experimental features

[michelle-clayton-work]

Agent mode's core behavior is ported. The meaningful missing capabilities are tool disabling and notification suppression. The tool input schema should also be aligned. Null-session, empty-list, and cancellation behavior need decisions about whether to preserve idiomatic Go behavior or match .NET exactly.

[michelle-clayton-work]

The .NET background-agents harness is currently unported. Go has some lower-level agent delegation and concurrency pieces, but the provider, tools, task state, waiting, continuation, cleanup, and session lifecycle are missing.

[michelle-clayton-work]

File Access, File Memory, and File Store are also missing from the Go side.

The order I will investigate the missing components is:

• ToolApproval audit
• Todo audit
• Loop audit
• FileStore
• FileMemory
• FileAccess

[michelle-clayton-work]

ToolApproval audit findings:

• in AlwaysApproveToolApprovalResposneContent, go does not throw if innerResposne is null which is potentially not necessary since its use case always guarantee a non-null (although since its a struct a user coudl somehwo manually set it to null which we might want tosafeguard because in the current state it would ignore null but .NET throws)
• AllToolsAutoApprovalRule() is missing in go implementation
• Go includes DisableNoneApprovalRequiredToolBypassing and DisableApprovalResponseBinding in the ToolApprovalAgentOptions class (.NET removed these functionalities so we should too)
• In ToolApprovalRequestContentExtensions there was a function that was commented as deprecated, can we drop that now?
• In ToolapprovalRule, we should consider aligning the rule struct visbiities

[michelle-clayton-work]

Also need to port https://github.com/microsoft/agent-framework/blob/main/dotnet/src/Microsoft.Agents.AI.Harness/HarnessAgent.cs -- consider modeling as middleware

[michelle-clayton-work]

Todo audit findings:

• consider aligning the ItemInput and CompleteInput visbilities
• Align formatTodoListMessage (don't append trailing newline and don't display whitespace only descriptions)

[michelle-clayton-work]

Loop audit findings:

• every class is tagged as experimental so should not need to port anything yet for 2.0