Remove warnings from build (#29)

* Remove warnings from build

* More fixes.

* Using const for transport types

src/mcpdotnet/Protocol/Types/GetPromptResult.cs

@@ -16,5 +16,5 @@ public class GetPromptResult
     /// The prompt or prompt template that the server offers.
     /// </summary>
     [System.Text.Json.Serialization.JsonPropertyName("messages")]
-    public List<PromptMessage> Messages { get; set; } = new();
+    public List<PromptMessage> Messages { get; set; } = [];
 }