Add DynamicallyAccessedMembers annotation to LayoutAttribute.LayoutType property

[Copilot]

Summary

Fixes the trimming annotation on LayoutAttribute.LayoutType property to properly propagate trimming information from the constructor parameter.

Problem

The LayoutAttribute constructor parameter had the [DynamicallyAccessedMembers(Component)] annotation, but the LayoutType property that stores this value did not have the annotation. This caused consumers of the attribute to receive false trimming warnings when accessing the property:

// Constructor parameter is properly annotated
public LayoutAttribute([DynamicallyAccessedMembers(Component)] Type layoutType)
{
    LayoutType = layoutType; // Assignment to property without annotation
    // ...
}

// Property without annotation - causes warnings for consumers
public Type LayoutType { get; private set; }

Solution

Added the [DynamicallyAccessedMembers(Component)] annotation to the LayoutType property to ensure trimming information flows properly:

[DynamicallyAccessedMembers(Component)]
public Type LayoutType { get; private set; }

This ensures that:

• The trimming analyzer understands that all members of the component type should be preserved
• Consumers can access LayoutType without false warnings
• The annotation on the property matches the constructor parameter, maintaining consistency

Testing

• All 1,174 existing tests in the Components test suite pass
• Build completes without errors or warnings
• No security issues detected by CodeQL

Fixes #[issue_number]

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[Blazor] LayoutAttribute.LayoutType should have proper trimming annotation</issue_title>
<issue_description>The LayoutAttribute property in Microsoft.AspNetCore.Components.LayoutAttribute should also have [DynamicallyAccessedMembers(Component)] annotation. Currently, only the constructor parameter is annotated, which gives consumers of the attribute a false warning when accessing the property.

aspnetcore/src/Components/Components/src/LayoutAttribute.cs

Line 39 in d434929

public Type LayoutType { get; private set; }

Should be:

[DynamicallyAccessedMembers(Component)]
public Type LayoutType { get; private set; }
```</issue_description>

## Comments on the Issue (you are @copilot in this section)

<comments>
</comments>

Fixes #64119

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[Copilot]

Pull Request Overview

This PR adds the [DynamicallyAccessedMembers(Component)] annotation to the LayoutAttribute.LayoutType property to properly propagate trimming information from the constructor parameter. This fix prevents false trimming warnings for consumers accessing the property.

• Adds the missing trimming annotation to the LayoutType property
• Ensures consistency between constructor parameter and property annotations
• Resolves false warnings when consumers access the property value