fix: use 'ws' as the WebSockets binding key

The bindings spec and schema name the WebSockets binding 'ws', not 'websockets'.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

Author: bielu

src/ByteBard.AsyncAPI.Bindings/WebSockets/WebSocketsChannelBinding.cs

@@ -23,7 +23,7 @@ public class WebSocketsChannelBinding : ChannelBinding<WebSocketsChannelBinding>
         /// </summary>
         public AsyncApiJsonSchema Headers { get; set; }
 
-        public override string BindingKey => "websockets";
+        public override string BindingKey => "ws";
 
         protected override FixedFieldMap<WebSocketsChannelBinding> FixedFieldMap => new()
         {

test/ByteBard.AsyncAPI.Tests/Bindings/WebSockets/WebSocketBindings_Should.cs

@@ -16,7 +16,7 @@ public void V2_WebSocketChannelBinding_WithFilledObject_SerializesAndDeserialize
             var expected =
                 """
                 bindings:
-                  websockets:
+                  ws:
                     method: POST
                     query:
                       description: this mah query

test/ByteBard.AsyncAPI.Tests/Models/AsyncApiChannel_Should.cs

@@ -36,7 +36,7 @@ public void V2_AsyncApiChannel_WithWebSocketsBinding_Serializes()
         {
             var expected = """
                 bindings:
-                  websockets:
+                  ws:
                     method: POST
                     query:
                       properties: