Update UnbrandedGeneratorVersion to 1.0.0-alpha.20260319.4

[azure-sdk]

This PR updates the UnbrandedGeneratorVersion property in eng/centralpackagemanagement/Directory.Generation.Packages.props and the @typespec/http-client-csharp dependency in eng/packages/http-client-csharp/package.json to version 1.0.0-alpha.20260319.4.

Details

• TypeSpec commit that triggered this PR: microsoft/typespec@d3b7f61

Changes

• Updated eng/centralpackagemanagement/Directory.Generation.Packages.props UnbrandedGeneratorVersion property
• Updated eng/packages/http-client-csharp/package.json dependency version
• Ran npm install to update package-lock.json
• Ran eng/packages/http-client-csharp/eng/scripts/Generate.ps1 to regenerate test projects
• Generated emitter-package.json artifacts using tsp-client
• Regenerated SDK libraries using the unbranded emitter via dotnet msbuild /t:GenerateCode

This is an automated PR created by the TypeSpec publish pipeline.

[Copilot]

Pull request overview

This PR updates the repository’s pinned TypeSpec unbranded C# emitter version to 1.0.0-alpha.20260319.4 across central generation props and the TypeSpec generator package/artifact inputs used for SDK regeneration.

Changes:

• Bump UnbrandedGeneratorVersion to 1.0.0-alpha.20260319.4.
• Update @typespec/http-client-csharp dependency to 1.0.0-alpha.20260319.4 in the generator’s npm dependencies and generated emitter artifacts.
• Refresh the generated emitter package lock/artifact data to align with the new TypeSpec toolchain versions.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 2 comments.

File	Description
eng/packages/http-client-csharp/package.json	Updates the generator’s dependency on @typespec/http-client-csharp to the new alpha build.
eng/http-client-csharp-emitter-package.json	Updates the generated unbranded emitter artifact dependency versions (including toolchain core).
eng/http-client-csharp-emitter-package-lock.json	Updates the generated lockfile for the unbranded emitter artifact to match the new dependency versions.
eng/centralpackagemanagement/Directory.Generation.Packages.props	Bumps the centrally pinned unbranded generator version used by repo generation workflows.

Files not reviewed (1)

• eng/http-client-csharp-emitter-package-lock.json: Language not supported

[Copilot]

@jorgerangel-msft I've opened a new pull request, #57298, to work on those changes. Once the pull request is ready, I'll request review from you.

[jorgerangel-msft]

@copilot lets regenerate all the unbranded libraries that use the SCM emitter https://github.com/Azure/azure-sdk-for-net/blob/main/doc/GeneratorMigration/Library_Inventory.md by running dotnet build /t:GenerateCode from their folder. Check in any updated files

[Copilot]

@jorgerangel-msft I've opened a new pull request, #57299, to work on those changes. Once the pull request is ready, I'll request review from you.

[jorgerangel-msft]

/check-enforcer override

[jorgerangel-msft]

Failing test is unrelated to the changes in this pr