feat: add reusable jobqueue library

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

tests/WorkerPool.test.ts

@@ -0,0 +1,26 @@
+import { WorkerPool } from '../src/index.js';
+import { waitFor } from './helpers.js';
+
+describe('WorkerPool', () => {
+  it('respects concurrency limits', async () => {
+    const pool = new WorkerPool(2);
+    let active = 0;
+    let maxActive = 0;
+
+    const tasks = Array.from({ length: 5 }, (_, index) =>
+      pool.run(async () => {
+        active += 1;
+        maxActive = Math.max(maxActive, active);
+        await new Promise((resolve) => {
+          setTimeout(resolve, 20 + index);
+        });
+        active -= 1;
+      }),
+    );
+
+    await Promise.all(tasks);
+    await waitFor(() => pool.activeCount === 0 && pool.pendingCount === 0);
+
+    expect(maxActive).toBe(2);
+  });
+});