Remove ExperimentalAttribute from official Extensions/Tasks/MRTR APIs and align MCPEXP001 usage (#1642)

src/ModelContextProtocol.Core/Protocol/ClientCapabilities.cs

@@ -1,5 +1,4 @@
 using System.ComponentModel;
-using System.Diagnostics.CodeAnalysis;
 using System.Text.Json.Serialization;
 using ModelContextProtocol.Client;
 using ModelContextProtocol.Server;
@@ -84,7 +83,6 @@ public sealed class ClientCapabilities
     /// interoperability. Clients advertise extension support via this field during the initialization handshake.
     /// </para>
     /// </remarks>
-    [Experimental(Experimentals.Extensions_DiagnosticId, UrlFormat = Experimentals.Extensions_Url)]
     [JsonIgnore]
     public IDictionary<string, object>? Extensions
     {

src/ModelContextProtocol.Core/Protocol/InputRequest.cs

@@ -1,4 +1,3 @@
-using System.Diagnostics.CodeAnalysis;
 using System.Text.Json;
 using System.Text.Json.Serialization;
 
@@ -20,7 +19,6 @@ namespace ModelContextProtocol.Protocol;
 /// parameters can be accessed via the typed accessor properties.
 /// </para>
 /// </remarks>
-[Experimental(Experimentals.Mrtr_DiagnosticId, UrlFormat = Experimentals.Mrtr_Url)]
 [JsonConverter(typeof(Converter))]
 public sealed class InputRequest
 {

src/ModelContextProtocol.Core/Protocol/InputRequiredException.cs

@@ -1,5 +1,3 @@
-using System.Diagnostics.CodeAnalysis;
-
 namespace ModelContextProtocol.Protocol;
 
 /// <summary>
@@ -54,7 +52,6 @@ namespace ModelContextProtocol.Protocol;
 /// }
 /// </code>
 /// </example>
-[Experimental(Experimentals.Mrtr_DiagnosticId, UrlFormat = Experimentals.Mrtr_Url)]
 public class InputRequiredException : Exception
 {
     /// <summary>

src/ModelContextProtocol.Core/Protocol/InputRequiredResult.cs

@@ -1,4 +1,3 @@
-using System.Diagnostics.CodeAnalysis;
 using System.Text.Json.Serialization;
 
 namespace ModelContextProtocol.Protocol;
@@ -22,7 +21,6 @@ namespace ModelContextProtocol.Protocol;
 /// This type is part of the Multi Round-Trip Requests (MRTR) mechanism defined in SEP-2322.
 /// </para>
 /// </remarks>
-[Experimental(Experimentals.Mrtr_DiagnosticId, UrlFormat = Experimentals.Mrtr_Url)]
 public sealed class InputRequiredResult : Result
 {
     /// <summary>

src/ModelContextProtocol.Core/Protocol/InputResponse.cs

@@ -1,4 +1,3 @@
-using System.Diagnostics.CodeAnalysis;
 using System.Text.Json;
 using System.Text.Json.Serialization;
 using System.Text.Json.Serialization.Metadata;
@@ -21,7 +20,6 @@ namespace ModelContextProtocol.Protocol;
 /// the corresponding <see cref="InputRequest.Method"/> key in the <see cref="InputRequiredResult.InputRequests"/> map.
 /// </para>
 /// </remarks>
-[Experimental(Experimentals.Mrtr_DiagnosticId, UrlFormat = Experimentals.Mrtr_Url)]
 [JsonConverter(typeof(Converter))]
 public sealed class InputResponse
 {

src/ModelContextProtocol.Core/Protocol/RequestParams.cs

@@ -1,4 +1,3 @@
-using System.Diagnostics.CodeAnalysis;
 using System.Text.Json.Nodes;
 using System.Text.Json.Serialization;
 
@@ -36,7 +35,6 @@ public abstract class RequestParams
     /// the value is the client's response to that input request.
     /// </para>
     /// </remarks>
-    [Experimental(Experimentals.Mrtr_DiagnosticId, UrlFormat = Experimentals.Mrtr_Url)]
     [JsonIgnore]
     public IDictionary<string, InputResponse>? InputResponses
     {
@@ -59,7 +57,6 @@ public abstract class RequestParams
     /// exact value without modification.
     /// </para>
     /// </remarks>
-    [Experimental(Experimentals.Mrtr_DiagnosticId, UrlFormat = Experimentals.Mrtr_Url)]
     [JsonIgnore]
     public string? RequestState
     {

src/ModelContextProtocol.Core/Protocol/ServerCapabilities.cs

@@ -1,5 +1,4 @@
 using System.ComponentModel;
-using System.Diagnostics.CodeAnalysis;
 using System.Text.Json.Serialization;
 using ModelContextProtocol.Server;
 
@@ -82,7 +81,6 @@ public sealed class ServerCapabilities
     /// interoperability. Servers advertise extension support via this field during the initialization handshake.
     /// </para>
     /// </remarks>
-    [Experimental(Experimentals.Extensions_DiagnosticId, UrlFormat = Experimentals.Extensions_Url)]
     [JsonIgnore]
     public IDictionary<string, object>? Extensions
     {