Create agent context

curl --request POST \
  --url https://api.wacht.dev/agent/contexts \
  --header 'Content-Type: application/x-www-form-urlencoded' \
  --cookie session_id= \
  --data 'title=Customer Support Conversation' \
  --data 'system_instructions=You are a helpful customer support assistant.'

{
  "status": 200,
  "message": "",
  "data": {
    "id": "123456789012345678",
    "deployment_id": "111111111111111111",
    "context_group": "support-agents",
    "title": "Customer Support Conversation",
    "system_instructions": "You are a helpful customer support assistant.",
    "status": "active",
    "message_count": 15,
    "created_at": "2024-01-15T10:30:00Z",
    "updated_at": "2024-01-15T11:30:00Z"
  },
  "session": {
    "id": "123456789012345678",
    "created_at": "2023-11-07T05:31:56Z",
    "updated_at": "2023-11-07T05:31:56Z"
  },
  "errors": [
    {
      "code": "INVALID_CREDENTIALS",
      "message": "Invalid credentials. Please try again."
    }
  ]
}