style(library): move conditional compilation directives above namespace and rename V3_0 to V30

Agent-Logs-Url: https://github.com/microsoft/OpenAPI.NET/sessions/0fac65d3-0bbb-44db-b82e-7648c8fb8f86

Co-authored-by: baywet <7905502+baywet@users.noreply.github.com>

Author: Copilot

src/Microsoft.OpenApi/Attributes/ExperimentalAttribute.cs

@@ -4,9 +4,9 @@
 // Polyfill for ExperimentalAttribute which is only available in .NET 8+.
 // Since the compiler queries for this attribute by name, having it source-included
 // is sufficient for the compiler to recognize it.
+#if !NET8_0_OR_GREATER
 namespace System.Diagnostics.CodeAnalysis
 {
-#if !NET8_0_OR_GREATER
     /// <summary>
     /// Indicates that an API is experimental and it may change in the future.
     /// </summary>
@@ -42,5 +42,5 @@ public ExperimentalAttribute(string diagnosticId)
         /// </summary>
         public string? UrlFormat { get; set; }
     }
-#endif
 }
+#endif

src/Microsoft.OpenApi/Services/OpenApiPathHelper.cs

@@ -27,7 +27,7 @@ public static class OpenApiPathHelper
         ],
         [OpenApiSpecVersion.OpenApi3_0] =
         [
-            new V3_0UnsupportedPathPolicy(),
+            new V30UnsupportedPathPolicy(),
         ],
     };
 
@@ -242,7 +242,7 @@ public bool TryGetVersionedPath(string[] segments, out string? result)
 /// Returns null for paths that have no equivalent in OpenAPI v3.0.
 /// Covers: webhooks (added in v3.1).
 /// </summary>
-internal sealed class V3_0UnsupportedPathPolicy : IOpenApiPathRepresentationPolicy
+internal sealed class V30UnsupportedPathPolicy : IOpenApiPathRepresentationPolicy
 {
     public bool TryGetVersionedPath(string[] segments, out string? result)
     {