Move IOperationReporter, ISnapshotModelProcessor and SnapshotModelProcessor to EFCore.Relational

[Copilot]

Fixes #37293

Relational providers reference EFCore.Relational but not EFCore.Design, so they could not derive from SnapshotModelProcessor or register a custom ISnapshotModelProcessor for provider-specific snapshot fixups. This relocates those design-time services down to EFCore.Relational.

Type moves (namespaces preserved → no using churn)

• IOperationReporter → EFCore.Relational/Design/Internal/
• ISnapshotModelProcessor, SnapshotModelProcessor → EFCore.Relational/Migrations/Internal/
• Concrete OperationReporter and IOperationReportHandler stay in EFCore.Design (Design-only concerns).

Supporting changes

• Moved the MultipleAnnotationConflict resource from DesignStrings to RelationalStrings (the processor can no longer reach DesignStrings).
• Added #pragma warning disable EF1001 around internal Model/ModelExtensions usage, since the EF analyzer runs in EFCore.Relational (it does not in EFCore.Design).
• Updated the linked-source path in ef.csproj and added an explicit EFCore.Relational reference to EFCore.Specification.Tests (which disables transitive references).

The default registration stays a TryAdd in DesignTimeServiceCollectionExtensions, which runs after provider design-time services — so a provider override now wins:

public class MyDesignTimeServices : IDesignTimeServices
{
    public void ConfigureDesignTimeServices(IServiceCollection services)
        => services.AddScoped<ISnapshotModelProcessor, MySnapshotModelProcessor>();
}

// where MySnapshotModelProcessor : SnapshotModelProcessor (now in EFCore.Relational)

[Copilot]

Pull request overview

This PR relocates key design-time migration snapshot services (IOperationReporter, ISnapshotModelProcessor, SnapshotModelProcessor) into EFCore.Relational so relational providers (which commonly reference EFCore.Relational but not EFCore.Design) can derive from/override snapshot processing for provider-specific fixups.

Changes:

• Moved IOperationReporter and snapshot processing abstractions/implementation into EFCore.Relational (namespaces preserved to avoid churn).
• Moved the MultipleAnnotationConflict resource from DesignStrings to RelationalStrings and updated usages/tests accordingly.
• Updated build/test infrastructure references (linked-source path in ef.csproj, explicit EFCore.Relational reference in specification tests) and updated the migrations agent skill doc.

Reviewed changes

Copilot reviewed 7 out of 11 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
test/EFCore.Specification.Tests/EFCore.Specification.Tests.csproj	Adds explicit EFCore.Relational reference needed due to non-transitive test setup.
test/EFCore.Design.Tests/Migrations/Design/SnapshotModelProcessorTest.cs	Updates expected warning message source from DesignStrings to RelationalStrings.
src/EFCore.Relational/Properties/RelationalStrings.resx	Adds MultipleAnnotationConflict resource to Relational.
src/EFCore.Relational/Properties/RelationalStrings.Designer.cs	Adds the strongly-typed accessor for MultipleAnnotationConflict.
src/EFCore.Relational/Migrations/Internal/SnapshotModelProcessor.cs	Switches warning string source to RelationalStrings and adds EF1001 suppression where needed.
src/EFCore.Relational/Migrations/Internal/ISnapshotModelProcessor.cs	Introduces the snapshot processor abstraction in Relational for provider overrides.
src/EFCore.Relational/Design/Internal/IOperationReporter.cs	Introduces IOperationReporter in Relational for broader provider accessibility.
src/EFCore.Design/Properties/DesignStrings.resx	Removes MultipleAnnotationConflict resource from Design.
src/EFCore.Design/Properties/DesignStrings.Designer.cs	Removes the strongly-typed accessor for MultipleAnnotationConflict.
src/ef/ef.csproj	Updates linked-source path for IOperationReporter to point to Relational.
.agents/skills/migrations/SKILL.md	Updates internal agent documentation to reflect the new locations/registration behavior.

Files not reviewed (2)

• src/EFCore.Design/Properties/DesignStrings.Designer.cs: Language not supported
• src/EFCore.Relational/Properties/RelationalStrings.Designer.cs: Language not supported

Comments suppressed due to low confidence (1)

src/EFCore.Relational/Migrations/Internal/SnapshotModelProcessor.cs:7

• using Microsoft.EntityFrameworkCore.Diagnostics; is redundant here because EFCore.Relational already provides this namespace via global <Using Include="Microsoft.EntityFrameworkCore.Diagnostics" /> in EFCore.Relational.csproj. Keeping it will typically trigger IDE0005 (unnecessary using) under analyzers.

[Copilot]

Pull request overview

Copilot reviewed 7 out of 11 changed files in this pull request and generated no new comments.

Files not reviewed (2)

• src/EFCore.Design/Properties/DesignStrings.Designer.cs: Language not supported
• src/EFCore.Relational/Properties/RelationalStrings.Designer.cs: Language not supported