Fix M.E.AI package refs

[stephentoub]

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull Request Overview

This PR fixes package references in Microsoft.Extensions.AI libraries by conditionally including certain System package dependencies only when the target framework is not .NET Core App. This optimization leverages the fact that .NET Core App already includes these packages in its base class libraries.

• Conditionally includes System.* package references only for non-.NET Core App targets
• Separates unconditional package references from conditional ones using distinct ItemGroup elements
• Applies consistent pattern across four Microsoft.Extensions.AI library projects

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
Microsoft.Extensions.AI.csproj	Separates System package references into conditional ItemGroup for non-.NET Core App targets
Microsoft.Extensions.AI.OpenAI.csproj	Moves System.Memory.Data and System.Text.Json to conditional ItemGroup
Microsoft.Extensions.AI.Ollama.csproj	Adds condition to existing ItemGroup for System package references
Microsoft.Extensions.AI.AzureAIInference.csproj	Separates System package references into conditional ItemGroup

[sebastienros]

This PR seems to be the reason the main branch builds are broken on SourceIndexStage1 job.

https://dev.azure.com/dnceng/internal/_build/results?buildId=2757536&view=logs&j=316d5c15-0c50-544e-8051-e6b14a1ab674&t=4e01507e-10cc-507d-f6d0-adc59e92bcb8

[stephentoub]

This PR seems to be the reason the main branch builds are broken on SourceIndexStage1 job.

https://dev.azure.com/dnceng/internal/_build/results?buildId=2757536&view=logs&j=316d5c15-0c50-544e-8051-e6b14a1ab674&t=4e01507e-10cc-507d-f6d0-adc59e92bcb8

I'm having trouble deciphering the dependency output there. @ericstj, it looks like something is referencing STJ 6.0 and S.D.DiagnosticSource 6.0 packages and that's causing a conflict?

[sebastienros]

@joperezr said he would take a look at it

[ericstj]

Something weird about the build of https://github.com/dotnet/extensions/blob/main/src/Packages/Microsoft.Internal.Extensions.DotNetApiDocs.Transport/Microsoft.Internal.Extensions.DotNetApiDocs.Transport.proj

I would expect it to get the latest System.Diagnostics.DiagnosticSource which is brought in transitively by the projects it references, but instead it's getting an older version.

Something fishy with how that project is set up. I see @joperezr already worked around a similar bug before 424e974

[stephentoub]

@sebastienros / @joperezr , did this get resolved?

[sebastienros]

From what I see, not resolved