HITL endpoints

POST /hitl/respond
X-Engine-Key: <key>
Content-Type: application/json

{
  "task_id": "task-001",
  "answer": "yes",
  "feedback": "Looks correct, go ahead.",
  "content_blocks": []
}

{
  "status": "resumed",
  "request_id": "hitl-..."
}

GET /hitl/pending
X-Engine-Key: <key>

{
  "pending": [
    {
      "request_id": "hitl-...",
      "task_id": "task-001",
      "kind": "permission",
      "question": "Should I delete /tmp/foo?",
      "created_at": "2026-04-27T12:34:56.000Z"
    }
  ]
}