test: split NWC protocol harness

vitest.config.ts

@@ -1,6 +1,13 @@
+import { fileURLToPath, URL } from 'node:url';
+
 import { defineConfig } from 'vitest/config';
 
 export default defineConfig({
+  resolve: {
+    alias: {
+      '@': fileURLToPath(new URL('./src', import.meta.url)),
+    },
+  },
   test: {
     // the tested modules are pure crypto/codec/protocol logic - node's own
     // WebCrypto (crypto.subtle) and fetch cover everything they need, no