Prefer HTTP/2 for pod streaming transport by default

[Copilot]

This change advances the websocket-to-HTTP/2 transition by making streaming connections default to HTTP/2 where supported, without changing the public streaming APIs (exec, attach, portforward). It keeps the current transport surface intact while shifting protocol preference to HTTP/2.

• Transport default update

  • WebSocketBuilder now sets ClientWebSocketOptions.HttpVersion to 2.0 on NET5_0_OR_GREATER.
  • This applies to existing streaming call paths that use WebSocketBuilder (including pod exec/attach/port-forward).

• Focused behavioral coverage

  • Added a targeted unit test in KubernetesExecTests (for NET5_0_OR_GREATER) asserting the builder defaults to HTTP/2.

public WebSocketBuilder()
{
#if NET5_0_OR_GREATER
    Options.HttpVersion = HttpVersion.Version20;
#endif
}

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• crl.comodoca.com
  • Triggering command: /home/REDACTED/work/csharp/.codeql-scratch/dbs/csharp/working/.dotnet/dotnet /home/REDACTED/work/csharp/.codeql-scratch/dbs/csharp/working/.dotnet/dotnet restore --no-dependencies /home/REDACTED/work/csharp/csharp/src/KubernetesClient.Classic/KubernetesClient.Classic.csproj --packages /home/REDACTED/work/csharp/.codeql-scratch/dbs/csharp/working/packages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal /p:TargetFrameworkRootPath=/home/REDACTED/work/csharp/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:NetCoreTargetingPackRoot=/home/REDACTED/work/csharp/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:AllowMissingPrunePackageData=true (dns block)
• idp.issuer.url
  • Triggering command: /usr/share/dotnet/dotnet /usr/share/dotnet/dotnet exec --runtimeconfig /home/REDACTED/work/csharp/csharp/tests/KubernetesClient.Tests/bin/Debug/net10.0/KubernetesClient.Tests.runtimeconfig.json --depsfile /home/REDACTED/work/csharp/csharp/tests/KubernetesClient.Tests/bin/Debug/net10.0/KubernetesClient.Tests.deps.json /home/REDACTED/work/csharp/csharp/tests/KubernetesClient.Tests/bin/Debug/net10.0/testhost.dll --port 41297 --endpoint 127.0.0.1:041297 --role client --parentprocessid 4555 --telemetryoptedin false (dns block)
  • Triggering command: /usr/share/dotnet/dotnet /usr/share/dotnet/dotnet exec --runtimeconfig /home/REDACTED/work/csharp/csharp/tests/KubernetesClient.Tests/bin/Debug/net8.0/KubernetesClient.Tests.runtimeconfig.json --depsfile /home/REDACTED/work/csharp/csharp/tests/KubernetesClient.Tests/bin/Debug/net8.0/KubernetesClient.Tests.deps.json /home/REDACTED/work/csharp/csharp/tests/KubernetesClient.Tests/bin/Debug/net8.0/testhost.dll --port 35773 --endpoint 127.0.0.1:035773 --role client --parentprocessid 4554 --telemetryoptedin false (dns block)
  • Triggering command: /usr/share/dotnet/dotnet /usr/share/dotnet/dotnet exec --runtimeconfig /home/REDACTED/work/csharp/csharp/tests/KubernetesClient.Tests/bin/Debug/net9.0/KubernetesClient.Tests.runtimeconfig.json --depsfile /home/REDACTED/work/csharp/csharp/tests/KubernetesClient.Tests/bin/Debug/net9.0/KubernetesClient.Tests.deps.json /home/REDACTED/work/csharp/csharp/tests/KubernetesClient.Tests/bin/Debug/net9.0/testhost.dll --port 35093 --endpoint 127.0.0.1:035093 --role client --parentprocessid 4553 --telemetryoptedin false (dns block)
• ocsp.comodoca.com
  • Triggering command: /home/REDACTED/work/csharp/.codeql-scratch/dbs/csharp/working/.dotnet/dotnet /home/REDACTED/work/csharp/.codeql-scratch/dbs/csharp/working/.dotnet/dotnet restore --no-dependencies /home/REDACTED/work/csharp/csharp/src/KubernetesClient.Classic/KubernetesClient.Classic.csproj --packages /home/REDACTED/work/csharp/.codeql-scratch/dbs/csharp/working/packages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal /p:TargetFrameworkRootPath=/home/REDACTED/work/csharp/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:NetCoreTargetingPackRoot=/home/REDACTED/work/csharp/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:AllowMissingPrunePackageData=true (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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[k8s-ci-robot]

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[tg123]

@copilot Could you please remove all websocket api, replace with http2 streaming? e.g. exec

[Copilot]

@copilot Could you please remove all websocket api, replace with http2 streaming? e.g. exec

I can do this, but to fully remove websocket APIs and switch exec/attach/port-forward to true HTTP/2 bidirectional streaming, this PR needs a broader breaking API refactor (IKubernetes surface + demuxer transport + tests/examples). Please confirm which scope you want in this PR: (1) breaking removal of websocket APIs now, or (2) add new HTTP/2 streaming APIs first and deprecate websocket APIs for one release.