Fix screen render mode from json to html for MCP compatibility

- Change default renderMode from json to html in screen execution service
- json render mode not supported by Moqui screen framework
- html mode allows web-dependent screens to render properly
- Simple screens can now render successfully in MCP context
- Web-dependent screens still fall back to URLs as expected

@@ -482,7 +482,7 @@
                         
                         // Now call the screen tool with proper user context
                         serviceResult = ec.service.sync().name("McpServices.execute#ScreenAsMcpTool")
-                            .parameters([screenPath: screenPath, parameters: arguments ?: [:], renderMode: "json"])
+                            .parameters([screenPath: screenPath, parameters: arguments ?: [:], renderMode: "html"])
                             .call()
                             
                     } finally {
@@ -1324,7 +1324,7 @@ try {
         <in-parameters>
             <parameter name="screenPath" required="true"/>
             <parameter name="parameters" type="Map"><description>Parameters to pass to the screen</description></parameter>
-            <parameter name="renderMode" default="json"><description>Render mode: json, text, csv, xml</description></parameter>
+            <parameter name="renderMode" default="html"><description>Render mode: text, html, xml, vuet, qvt</description></parameter>
         </in-parameters>
         <out-parameters>
             <parameter name="result" type="Map"/>