A retail company is building a customer-facing chatbot to respond to product inquiries. The business requirement states that every reply must maintain a warm, empathetic brand voice and consistently structure responses as a short greeting followed by the answer and a closing offer to help further. The team is using a general-purpose instruction-tuned LLM without fine-tuning access. During testing, responses vary widely in tone and format. Which prompt strategy best addresses this requirement with minimal engineering effort?