refactor(core): dedupe shared config and runtime helpers

src/test-utils/mock-http-response.ts

@@ -0,0 +1,25 @@
+import type { ServerResponse } from "node:http";
+
+export function createMockServerResponse(): ServerResponse & { body?: string } {
+  const headers: Record<string, string> = {};
+  const res: {
+    headersSent: boolean;
+    statusCode: number;
+    body?: string;
+    setHeader: (key: string, value: string) => unknown;
+    end: (body?: string) => unknown;
+  } = {
+    headersSent: false,
+    statusCode: 200,
+    setHeader: (key: string, value: string) => {
+      headers[key.toLowerCase()] = value;
+      return res;
+    },
+    end: (body?: string) => {
+      res.headersSent = true;
+      res.body = body;
+      return res;
+    },
+  };
+  return res as unknown as ServerResponse & { body?: string };
+}