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

ts/protocols/common/fragment-handler.ts

@@ -5,7 +5,7 @@
  * that may span multiple TCP packets.
  */
 
-import { Buffer } from 'buffer';
+import { Buffer } from 'node:buffer';
 
 /**
  * Fragment tracking information

ts/protocols/tls/sni/client-hello-parser.ts

@@ -1,4 +1,4 @@
-import { Buffer } from 'buffer';
+import { Buffer } from 'node:buffer';
 import { 
   TlsRecordType,
   TlsHandshakeType,

ts/protocols/tls/sni/sni-extraction.ts

@@ -1,4 +1,4 @@
-import { Buffer } from 'buffer';
+import { Buffer } from 'node:buffer';
 import { TlsExtensionType, TlsUtils } from '../utils/tls-utils.js';
 import {
   ClientHelloParser,

ts/protocols/websocket/utils.ts

@@ -2,7 +2,7 @@
  * WebSocket Protocol Utilities
  */
 
-import * as crypto from 'crypto';
+import * as crypto from 'node:crypto';
 import { WEBSOCKET_MAGIC_STRING } from './constants.js';
 import type { RawData } from './types.js';