Point obsolete diagnostic URLs to the #obsolete-apis section anchor

The list-of-diagnostics.md table rows are not headings, so per-ID
fragments like #mcp9005 and #mcp9003 do not resolve. Link to the
#obsolete-apis section heading instead, matching the MCP9004 entry.

Author: Tarek Mahmoud Sayed

src/Common/Obsoletions.cs

@@ -28,7 +28,7 @@ internal static class Obsoletions
 
     public const string RequestContextParamsConstructor_DiagnosticId = "MCP9003";
     public const string RequestContextParamsConstructor_Message = "Use the constructor overload that accepts a parameters argument.";
-    public const string RequestContextParamsConstructor_Url = "https://github.com/modelcontextprotocol/csharp-sdk/blob/main/docs/list-of-diagnostics.md#mcp9003";
+    public const string RequestContextParamsConstructor_Url = "https://github.com/modelcontextprotocol/csharp-sdk/blob/main/docs/list-of-diagnostics.md#obsolete-apis";
 
     public const string EnableLegacySse_DiagnosticId = "MCP9004";
     public const string EnableLegacySse_Message = "Legacy SSE transport has no built-in request backpressure and should only be used with completely trusted clients in isolated processes. Use Streamable HTTP instead.";
@@ -38,7 +38,7 @@ internal static class Obsoletions
     // deprecation. They share one diagnostic ID (MCP9005) so consumers can opt out with a single
     // suppression, while the feature-specific messages keep the diagnostics distinguishable.
     public const string Deprecated_DiagnosticId = "MCP9005";
-    public const string Deprecated_Url = "https://github.com/modelcontextprotocol/csharp-sdk/blob/main/docs/list-of-diagnostics.md#mcp9005";
+    public const string Deprecated_Url = "https://github.com/modelcontextprotocol/csharp-sdk/blob/main/docs/list-of-diagnostics.md#obsolete-apis";
     public const string DeprecatedRoots_Message = "The Roots feature is deprecated as of specification version 2026-07-28 and may be removed in a future version. See SEP-2577 for more information.";
     public const string DeprecatedSampling_Message = "The Sampling feature is deprecated as of specification version 2026-07-28 and may be removed in a future version. See SEP-2577 for more information.";
     public const string DeprecatedLogging_Message = "The Logging feature is deprecated as of specification version 2026-07-28 and may be removed in a future version. See SEP-2577 for more information.";