fix: default transport to stdio if not provided

- Set default StdioServerTransport when transport not specified in config
- Fixes MCP server initialization issue preventing tool registration

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

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

Author: sapientpants

src/server/mcp-server.ts

@@ -84,10 +84,8 @@ export class DeepSourceMCPServer {
       this.registerDefaultTools();
     }
 
-    // Set transport if provided
-    if (this.config.transport) {
-      this.transport = this.config.transport;
-    }
+    // Set transport (default to stdio if not provided)
+    this.transport = this.config.transport || new StdioServerTransport();
   }
 
   /**