Change SupportedProtocolVersions from ICollection<string> to IReadOnlyList<string>

Co-authored-by: stephentoub <2642209+stephentoub@users.noreply.github.com>

Author: Copilot

src/ModelContextProtocol.Core/Server/DestinationBoundMcpServer.cs

@@ -12,7 +12,7 @@ internal sealed class DestinationBoundMcpServer(McpServerImpl server, ITransport
     public override McpServerOptions ServerOptions => server.ServerOptions;
     public override IServiceProvider? Services => server.Services;
     public override LoggingLevel? LoggingLevel => server.LoggingLevel;
-    public override ICollection<string> SupportedProtocolVersions => server.SupportedProtocolVersions;
+    public override IReadOnlyList<string> SupportedProtocolVersions => server.SupportedProtocolVersions;
 
     public override ValueTask DisposeAsync() => server.DisposeAsync();
 

src/ModelContextProtocol.Core/Server/McpServer.cs

@@ -58,7 +58,7 @@ public abstract partial class McpServer : McpSession
     /// <summary>
     /// Gets the protocol versions supported by this server implementation.
     /// </summary>
-    public abstract ICollection<string> SupportedProtocolVersions { get; }
+    public abstract IReadOnlyList<string> SupportedProtocolVersions { get; }
 
     /// <summary>
     /// Runs the server, listening for and handling client requests.

src/ModelContextProtocol.Core/Server/McpServerImpl.cs

@@ -156,7 +156,7 @@ void Register<TPrimitive>(McpServerPrimitiveCollection<TPrimitive>? collection,
     public override LoggingLevel? LoggingLevel => _loggingLevel?.Value;
 
     /// <inheritdoc />
-    public override ICollection<string> SupportedProtocolVersions => McpSessionHandler.SupportedProtocolVersions;
+    public override IReadOnlyList<string> SupportedProtocolVersions => McpSessionHandler.SupportedProtocolVersions;
 
     /// <inheritdoc />
     public override async Task RunAsync(CancellationToken cancellationToken = default)

tests/ModelContextProtocol.Tests/Server/McpServerTests.cs

@@ -938,7 +938,7 @@ public override Task<JsonRpcResponse> SendRequestAsync(JsonRpcRequest request, C
         public override Implementation? ClientInfo => throw new NotImplementedException();
         public override IServiceProvider? Services => throw new NotImplementedException();
         public override LoggingLevel? LoggingLevel => throw new NotImplementedException();
-        public override ICollection<string> SupportedProtocolVersions => throw new NotImplementedException();
+        public override IReadOnlyList<string> SupportedProtocolVersions => throw new NotImplementedException();
         public override Task SendMessageAsync(JsonRpcMessage message, CancellationToken cancellationToken = default) =>
             throw new NotImplementedException();
         public override Task RunAsync(CancellationToken cancellationToken = default) =>