Simplify default HTTP (CoplayDev#495)

* The default URL is already set when we call the function

* Remove placeholer for HTTP URL in the UI

When we load the UI, we use `HttpEndpointUtility.GetBaseUrl()`, so we don't need this

Author: msanatan

MCPForUnity/Editor/Services/Transport/Transports/WebSocketTransportClient.cs

@@ -703,11 +703,6 @@ private async Task AttemptReconnectAsync(CancellationToken token)
 
         private static Uri BuildWebSocketUri(string baseUrl)
         {
-            if (string.IsNullOrWhiteSpace(baseUrl))
-            {
-                baseUrl = "http://localhost:8080";
-            }
-
             if (!Uri.TryCreate(baseUrl, UriKind.Absolute, out var httpUri))
             {
                 throw new InvalidOperationException($"Invalid MCP base URL: {baseUrl}");

MCPForUnity/Editor/Windows/Components/Connection/McpConnectionSection.uxml

@@ -9,7 +9,7 @@
             </ui:VisualElement>
             <ui:VisualElement class="setting-row" name="http-url-row">
                 <ui:Label text="HTTP URL:" class="setting-label" />
-                <ui:TextField name="http-url" class="url-field" placeholder-text="http://localhost:8080" />
+                <ui:TextField name="http-url" class="url-field" />
             </ui:VisualElement>
             <ui:VisualElement name="http-server-command-section" class="manual-config-content">
                 <ui:Label text="Use this command to launch the server manually:" class="config-label" />