dotnet: add live TypeScript session conformance

[Josh (joshmouch)]

Summary

Add a hermetic real-socket interoperability lane between the current first-party .NET client and the repository-local TypeScript session reducer.

The test proves three runtime obligations that static fixture replay does not cover:

1. A real ClientWebSocket connection performs JSON-RPC initialize and negotiates the current protocol version.
2. The .NET client seeds session state from InitializeResult snapshots.
3. Four streamed action notifications converge structurally after the TypeScript host applies the canonical sessionReducer and the .NET client applies the handwritten C# Reducers.

The host binds to an ephemeral 127.0.0.1 port, has bounded readiness and shutdown, and is typechecked in CI. It uses only repository-local sources and current project references: no published package, absolute developer path, symlink, OpenAgency, Conflux, or external service.

Validation

• interoperability host TypeScript check
• change-fragment verification: 21 fragments
• AgentHostProtocol.Abstractions release build: 0 warnings/errors
• AgentHostProtocol release build: 0 warnings/errors
• AgentHostProtocol.Tests release build: 0 warnings/errors
• targeted real-socket test: 1 passed in 549 ms
• complete .NET suite: 536 passed, 0 failed, 0 skipped
• dotnet whitespace format verification
• owned host process cleanup: session-host-clean
• git diff --check

The build was partitioned by dependency layer so each finite validation command remains bounded; this does not weaken the complete test suite gate.

[Connor Peet (connor4312)]

Node has a built-in WebSocket client now if we want to use that, I am also not opposed to just having a dev dependency here on the ws package for the server side