refactor: extract magic numbers to named constants

Frontend: choreography selection ratios, morph trigger chances,
creator cameo/ultimate chances, dodge/counter probabilities.
Server: HP, K-factors, Elo divisor, tier thresholds, fight loop interval.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/engine/fight-loop.ts

@@ -1,3 +1,4 @@
+import { FIGHT_LOOP_INTERVAL_MS, ELO_MATCHING_RANDOMNESS } from '../lib/constants.js'
 import { db, schema } from '../db/index.js'
 import { runMockFight } from './mock.js'
 import { eq } from 'drizzle-orm'
@@ -31,7 +32,7 @@ export interface FightLoopOptions {
 
 export async function startFightLoop(options: FightLoopOptions = {}): Promise<void> {
   const {
-    intervalMs = 8000,
+    intervalMs = FIGHT_LOOP_INTERVAL_MS,
     maxFights = Infinity,
     matchmakingStyle = 'mixed',
     onFightStart,
@@ -161,8 +162,8 @@ function pickMatchup(
     const bot = pick(bots)
     const others = bots.filter(b => b.id !== bot.id)
     others.sort((a, b) => {
-      const diffA = Math.abs(a.eloRating - bot.eloRating) + Math.random() * 150
-      const diffB = Math.abs(b.eloRating - bot.eloRating) + Math.random() * 150
+      const diffA = Math.abs(a.eloRating - bot.eloRating) + Math.random() * ELO_MATCHING_RANDOMNESS
+      const diffB = Math.abs(b.eloRating - bot.eloRating) + Math.random() * ELO_MATCHING_RANDOMNESS
       return diffA - diffB
     })
     return [bot, others[0]]

server/src/engine/mock.ts

@@ -1,3 +1,4 @@
+import { STARTING_HP } from '../lib/constants.js'
 import { nanoid } from 'nanoid'
 import { logger } from '../lib/logger.js'
 import { createHash, randomBytes } from 'crypto'
@@ -433,8 +434,8 @@ export async function runMockFight(botAId: string, botBId: string): Promise<stri
     createdAt: now,
   })
 
-  let hpA = 200
-  let hpB = 200
+  let hpA = STARTING_HP
+  let hpB = STARTING_HP
   let comboA = 0
   let comboB = 0
   let winnerId: string | null = null

server/src/engine/orchestrator.ts

@@ -35,9 +35,7 @@ interface WebhookResponse {
   error: boolean
 }
 
-const MAX_ROUNDS = 10
-const KO_THRESHOLD = 0
-const MAX_RESPONSE_BYTES = 10 * 1024 // 10KB
+import { MAX_ROUNDS, KO_THRESHOLD, MAX_RESPONSE_BYTES, STARTING_HP, ELO_K_FACTOR, ELO_K_FACTOR_MOCK } from '../lib/constants.js'
 
 // Track bots currently in a fight to prevent concurrent fights
 const activeFighters = new Set<string>()
@@ -333,8 +331,8 @@ async function trackWebhookResult(botId: string, webhookUrl: string, succeeded:
 }
 
 async function executeFightRounds(fightId: string, botA: BotRecord, botB: BotRecord, arena: Arena, mode: 'free' | 'ranked' = 'free'): Promise<void> {
-  let hpA = 200
-  let hpB = 200
+  let hpA = STARTING_HP
+  let hpB = STARTING_HP
   let comboA = 0
   let comboB = 0
   let winnerId: string | null = null
@@ -447,13 +445,13 @@ async function executeFightRounds(fightId: string, botA: BotRecord, botB: BotRec
 
   const winnerName = winnerId === botA.id ? botA.name : winnerId === botB.id ? botB.name : 'nobody'
   const isPerfect = winnerId && (
-    (winnerId === botA.id && hpA === 200) ||
-    (winnerId === botB.id && hpB === 200)
+    (winnerId === botA.id && hpA === STARTING_HP) ||
+    (winnerId === botB.id && hpB === STARTING_HP)
   )
 
   // Finalize fight + update bot stats atomically
   const isMockFight = isMockBot(botA.webhookUrl) || isMockBot(botB.webhookUrl) || isClassicBot(botA.webhookUrl) || isClassicBot(botB.webhookUrl)
-  const kFactor = isMockFight ? 12 : 32 // Dampened Elo for mock/classic fights
+  const kFactor = isMockFight ? ELO_K_FACTOR_MOCK : ELO_K_FACTOR
   let winnerEloChange = 0
   let loserEloChange = 0
   let newWinnerEloFinal = 0

server/src/engine/scoring.ts

@@ -1,3 +1,4 @@
+import { ELO_DIVISOR, TIER_THRESHOLDS } from '../lib/constants.js'
 import type { Challenge } from './challenges.js'
 import { pick } from '../lib/utils.js'
 import { checkAnswer } from './answers.js'
@@ -523,7 +524,7 @@ export function calculateElo(
   loserElo: number,
   k: number = 32,
 ): { newWinnerElo: number; newLoserElo: number } {
-  const expectedWinner = 1 / (1 + Math.pow(10, (loserElo - winnerElo) / 400))
+  const expectedWinner = 1 / (1 + Math.pow(10, (loserElo - winnerElo) / ELO_DIVISOR))
   const expectedLoser = 1 - expectedWinner
 
   return {
@@ -534,13 +535,10 @@ export function calculateElo(
 
 // Tier calculation
 export function calculateTier(elo: number, wins: number): number {
-  if (elo >= 1900 && wins >= 40) return 6  // Legend
-  if (elo >= 1700 && wins >= 25) return 5  // Diamond
-  if (elo >= 1500 && wins >= 15) return 4  // Platinum
-  if (elo >= 1350 && wins >= 7) return 3   // Gold
-  if (elo >= 1200 && wins >= 3) return 2   // Silver
-  if (wins >= 1) return 1                   // Bronze
-  return 0                                  // Baby
+  for (const t of TIER_THRESHOLDS) {
+    if (elo >= t.elo && wins >= t.wins) return t.tier
+  }
+  return 0  // Baby
 }
 
 export const TIER_NAMES = ['BABY', 'BRONZE', 'SILVER', 'GOLD', 'PLATINUM', 'DIAMOND', 'LEGEND'] as const