Make the .NET library NativeAOT compatible

[stephentoub]

• Enabled AOT analyzers
• Disabled STJ reflection in the test project (to help vet NAOT correctness)
• Use source generation for all types that may be serialized
• Remove all use of anonymous types
• Removed <autogenerated/> from the source generated code, as it was suppressing the analyzers
• Added support for propagating StreamJsonRpc's tracing to the CopilotClient's ILogger. I used this for debugging and decided to leave it
• Updated StreamJsonRpc to a newly published version on nuget to pick up NativeAOT fixes
• Cleaned up some formatting in the session types generator, in particular using a file-scoped namespace and removing the top-level indentation

[Copilot]

Pull request overview

Updates the .NET SDK to be NativeAOT-friendly by removing reflection/anonymous-type usage in JSON paths and introducing System.Text.Json source generation for RPC + model types.

Changes:

• Switch RPC + model serialization to STJ source-generated contexts and remove anonymous request objects.
• Regenerate session event types with file-scoped namespace + source-gen JsonSerializerContext.
• Update tests to disable STJ reflection and add test-only serializer contexts; bump StreamJsonRpc.

Reviewed changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
nodejs/scripts/generate-csharp-session-types.ts	Updates the C# session-types generator to emit file-scoped namespace output and a source-gen JsonSerializerContext.
dotnet/test/ToolsTests.cs	Passes explicit serializer options for tool invocation and adds a test JsonSerializerContext.
dotnet/test/Harness/CapiProxy.cs	Replaces anonymous request payloads and switches HttpClient JSON calls to source-gen type info.
dotnet/test/GitHub.Copilot.SDK.Test.csproj	Disables reflection-based STJ serialization to validate NativeAOT compatibility in tests.
dotnet/src/Types.cs	Adds a TypesJsonContext with [JsonSerializable] entries for core SDK types (incl. Ping types).
dotnet/src/Session.cs	Removes anonymous RPC payloads and adds SessionJsonContext for request/response types.
dotnet/src/GitHub.Copilot.SDK.csproj	Marks the library as AOT compatible and updates StreamJsonRpc.
dotnet/src/Generated/SessionEvents.cs	Regenerated session events with file-scoped namespace and a source-gen context.
dotnet/src/Client.cs	Updates JsonRpc formatter setup for NativeAOT, removes attribute-based RPC target wiring, and adds trace forwarding to ILogger.

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[SteveSandersonMS]

Thanks, this looks great!