Docker sandbox real test + cloud merge status endpoint

- DockerExecutor: extra mounts (host.py work/state, repo, codex-home
  at same paths), worker --docker-extra-mounts, container user
  configurable; Dockerfile copies codex-resources beside the codex
  binary and puts bwrap on PATH (previous /usr/local/lib layout
  made codex report bubblewrap unavailable inside the container).
- Real Docker task on external host: triple added in ~18s, merged
  inside a container, main repo now add+mul2+triple, --rm cleanup.
  Honest boundary: this host/kernel forbids unprivileged user
  namespaces, so bwrap fails on host and in containers; production
  mode here is Docker isolation + inner danger-full-access, not
  double sandboxing.
- Cloud merge status: POST /tasks/{id}/merge syncs status only
  (merge itself stays with host.py merge); completed -> merged,
  maintainer+ (approve_merge), other states and repeat calls 409,
  audit merge_task. Tests: cloud 223, host 27, all passing.

cloud/tests/test_queue_sandbox.py

@@ -189,12 +189,29 @@ class TestExecutors(unittest.TestCase):
             self.assertIn("docker not available", str(ctx.exception))
             # 报错而不是返回 local 结果：绝不静默降级为本地执行
 
-    def test_docker_executor_with_docker_is_placeholder_failure(self):
-        with mock.patch("sandbox.shutil.which", return_value="/usr/bin/docker"):
-            result = DockerExecutor().execute({"id": "t1"})
+    def test_docker_executor_with_docker_runs_container(self):
+        seen = []
+
+        def fake_runner(cmd, timeout=None):
+            seen.append(cmd)
+            return SimpleNamespace(returncode=0, stdout="ok-status")
+
+        with mock.patch("sandbox.shutil.which",
+                        return_value="/usr/bin/docker"):
+            executor = DockerExecutor(
+                "/fake/host.py", runner=fake_runner,
+                env={"XCM_API_KEY": "placeholder-not-a-real-key"})
+            result = executor.execute({"id": "t1", "worktree": "/tmp/wt1"})
         self.assertEqual(result["executor"], "docker")
-        self.assertEqual(result["status"], "failed")
-        self.assertNotEqual(result["executor"], "local")
+        self.assertEqual(result["status"], "completed")
+        self.assertEqual(seen[0][0:2], ["docker", "run"])
+        self.assertIn("--rm", seen[0])
+        self.assertIn("/tmp/wt1:/work", seen[0])
+        self.assertIn("/fake:/app:ro", seen[0])
+        # -e 只传名，值绝不出现在命令列表里。
+        self.assertIn("XCM_API_KEY", seen[0])
+        self.assertNotIn("placeholder-not-a-real-key", seen[0])
+        self.assertNotIn("placeholder-not-a-real-key", " ".join(seen[0]))
 
     def test_cloud_executor_raises_with_cloud_account(self):
         with self.assertRaises(RuntimeError) as ctx: