Fix indentation of domain and prefersBorder in UiResourceMeta example

The domain and prefersBorder properties are now properly indented to be
at the same hierarchical level as csp within the ui object.

Addresses PR comment:
https://github.com/modelcontextprotocol/ext-apps/pull/5#discussion_r2553064940

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

specification/draft/apps.mdx

@@ -175,8 +175,8 @@ The resource content is returned via `resources/read`:
           connect_domains?: string[];  // Origins for fetch/XHR/WebSocket
           resource_domains?: string[]; // Origins for images, scripts, etc
         };
-      domain?: string;
-      prefersBorder?: boolean;
+        domain?: string;
+        prefersBorder?: boolean;
       };
     };
   }];