.NET: fix: preserve Foreach record values

[he-yufeng]

Fixes #6183.

Summary

• preserve each RecordDataValue as a full record when Foreach materializes table rows
• add a regression test for a multi-field row so the loop value exposes both fields

To verify

• dotnet test --project tests\Microsoft.Agents.AI.Workflows.Declarative.UnitTests\Microsoft.Agents.AI.Workflows.Declarative.UnitTests.csproj -f net10.0 -v Normal --filter-class Microsoft.Agents.AI.Workflows.Declarative.UnitTests.ObjectModel.ForeachExecutorTest
• dotnet test --project tests\Microsoft.Agents.AI.Workflows.Declarative.UnitTests\Microsoft.Agents.AI.Workflows.Declarative.UnitTests.csproj -f net472 -v Normal --filter-class Microsoft.Agents.AI.Workflows.Declarative.UnitTests.ObjectModel.ForeachExecutorTest
• dotnet format agent-framework-dotnet.slnx --verify-no-changes --no-restore --include src\Microsoft.Agents.AI.Workflows.Declarative\ObjectModel\ForeachExecutor.cs tests\Microsoft.Agents.AI.Workflows.Declarative.UnitTests\ObjectModel\ForeachExecutorTest.cs
• git diff --check

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Fixes a bug in ForeachExecutor where iterating over a TableDataValue only exposed the first field of each record instead of the full record.

Changes:

• Replace value.Properties.Values.First().ToFormula() with value.ToFormula() so the full record is yielded per iteration.
• Add a unit test verifying multi-field records expose all fields via the loop variable.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
dotnet/src/Microsoft.Agents.AI.Workflows.Declarative/ObjectModel/ForeachExecutor.cs	Yield full record (not just first property) when iterating a table.
dotnet/tests/Microsoft.Agents.AI.Workflows.Declarative.UnitTests/ObjectModel/ForeachExecutorTest.cs	Adds test asserting all record fields are accessible from the iteration variable.