feat(worker): run terminals and agent turns as the box user

apps/agent-worker/tests/unit/user-container.test.ts

@@ -22,6 +22,20 @@ describe('box registry', () => {
     vi.clearAllMocks();
   });
 
+  test('passes an onCreated hook so a fresh box gets its user initialized', async () => {
+    const module = await load();
+    const docker = await import('../../src/runtime/docker');
+    await module.acquireUserBox({
+      username: 'ada',
+      workdir: '/w',
+      containerHome: '/home/ada',
+    });
+    const call = vi.mocked(docker.ensureUserContainer).mock.calls[0]?.[0] as {
+      onCreated?: unknown;
+    };
+    expect(call.onCreated).toBeTypeOf('function');
+  });
+
   test('re-ensures the container on every acquire so an externally removed box self-heals', async () => {
     const module = await load();
     const docker = await import('../../src/runtime/docker');