Fix missing comma in prompt listing causing build/test failure

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: chughtapan

packages/server/src/server/mcp.ts

@@ -530,7 +530,7 @@ export class McpServer {
                             name,
                             title: prompt.title,
                             description: prompt.description,
-                            arguments: prompt.argsSchema ? promptArgumentsFromStandardSchema(prompt.argsSchema) : undefined
+                            arguments: prompt.argsSchema ? promptArgumentsFromStandardSchema(prompt.argsSchema) : undefined,
                             _meta: prompt._meta
                         };
                     })