feat: complete TASK-WP0-01 toolchain skeleton

apps/worker/src/worker.ts

@@ -0,0 +1,13 @@
+import { parentPort } from "node:worker_threads";
+
+export function handleWorkerProbe(message: unknown) {
+  return message === "ping" ? "pong" : null;
+}
+
+const workerPort = parentPort;
+
+if (workerPort) {
+  workerPort.on("message", (message: unknown) => {
+    workerPort.postMessage(handleWorkerProbe(message));
+  });
+}