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/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