Validation: skip static properties in generated model traversal

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Skip static properties during validation traversal

Description

Minimal API validation could recurse indefinitely when generated metadata included static self-referential properties (e.g., public static MyModel TheAnswer => new()). This change ensures static properties are ignored at runtime traversal, preventing false circular-depth failures.

• Runtime behavior change

  • Added a static-getter guard in ValidatablePropertyInfo.ValidateAsync to skip validation for static properties.

• Regression coverage

  • Added Validate_IgnoresStaticProperties to verify static self-referential metadata does not recurse.
  • Added Validate_ThrowsForRecursiveInstanceProperties as a control to confirm instance recursion behavior is unchanged (max-depth still enforced).

var property = DeclaringType.GetProperty(Name)
    ?? throw new InvalidOperationException(...);

if (property.GetMethod?.IsStatic is true)
{
    return;
}