fix(core): use node: scoped builtin imports and add route unit tests

ts/core/utils/socket-tracker.ts

@@ -3,7 +3,7 @@
  * Provides standardized socket cleanup with proper listener and timer management
  */
 
-import type { Socket } from 'net';
+import type { Socket } from 'node:net';
 
 export type SocketTracked = {
   cleanup: () => void;