OpenAI SDK instantiated at module level crashes Next.js build

// ❌ Crashes at build time
import OpenAI from 'openai'
export const openai = new OpenAI({ apiKey: process.env.OPENAI_API_KEY })

// ✅ Lazy — only instantiated when first used at runtime
import OpenAI from 'openai'
let _client: OpenAI | null = null

export function getOpenAIClient(): OpenAI {
  if (!_client) {
    _client = new OpenAI({ apiKey: process.env.OPENAI_API_KEY ?? '' })
  }
  return _client
}

// Optional: keep named export working for existing callers
export const openai = new Proxy({} as OpenAI, {
  get(_target, prop) {
    return (getOpenAIClient() as any)[prop]
  },
})