.NET: Fix local variable naming conventions

[XiongHaoTrigger]

Motivation and Context

In src/Microsoft.Agents.AI/Evaluation/LocalEvaluator.cs, the local variable EvalCheckResult in the EvaluateAsync method uses PascalCase naming, which violates the C# naming convention — local variables should use camelCase. PascalCase for a local variable can mislead reviewers into thinking it's a type name, reducing readability.

Description

Fixed the local variable name in src/Microsoft.Agents.AI/Evaluation/LocalEvaluator.cs from EvalCheckResult to evalCheckResult (6 occurrences in the EvaluateAsync method) to conform to .NET camelCase naming conventions. This is a pure style fix with no logic changes.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.；

[Copilot]

Pull request overview

Note

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

Aligns local evaluation metric creation with standard C# naming conventions by renaming a local variable used to store check results.

Changes:

• Renamed EvalCheckResult to evalCheckResult for camelCase local variable convention.
• Updated all subsequent references to the renamed variable in metric construction and interpretation.