score()

churn.score(
  userId: string,
  options?: ScoreOptions
): Promise<RiskScore>

interface RiskScore {
  userId: string
  score: number         // 0.0 (healthy) → 1.0 (churning)
  tier: RiskTier        // 'low' | 'medium' | 'high'
  signals: string[]     // reasons driving the score
  recommendation: string
}

const risk = await churn.score('user_123')

console.log(risk.score)          // 0.82
console.log(risk.tier)           // 'high'
console.log(risk.signals)        // ['no_login_7d', 'support_spike', 'export_all_data']
console.log(risk.recommendation) // 'This user is at high risk. Reach out immediately.'

const risk = await churn.score(userId)

switch (risk.tier) {
  case 'high':
    await sendSlackAlert({ userId, score: risk.score, signals: risk.signals })
    await queueOutreachEmail(userId, 'high_risk_template')
    break
  case 'medium':
    await queueOutreachEmail(userId, 'check_in_template')
    break
  case 'low':
    // healthy — no action
    break
}

// Run daily for all active users
const users = await db.getActiveUsers()

for (const user of users) {
  const risk = await churn.score(user.id)
  if (risk.tier === 'high') {
    await alertCustomerSuccess(user.id, risk)
  }
}

const controller = new AbortController()
const timeout = setTimeout(() => controller.abort(), 3000)

try {
  const risk = await churn.score('user_123', { signal: controller.signal })
  return risk
} finally {
  clearTimeout(timeout)
}