feat: show rejoin link when bot is already in a fight

- Track active fight IDs per bot in orchestrator (Set → Map)
- Return fightId in "already in fight" error responses (409)
- Frontend shows "REJOIN FIGHT" link instead of generic error

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

server/src/routes/fights.ts

@@ -7,7 +7,7 @@ import { eq, desc, inArray } from 'drizzle-orm'
 import { ARENAS } from '../engine/arenas.js'
 import { runMockFight, isClassicBot } from '../engine/mock.js'
 import { startFightLoop } from '../engine/fight-loop.js'
-import { runFight, runFightAsync, isInFight } from '../engine/orchestrator.js'
+import { runFight, runFightAsync, isInFight, getActiveFightId } from '../engine/orchestrator.js'
 import { fightEvents } from '../engine/events.js'
 import { botRateLimit } from '../middleware/rate-limit.js'
 import { getPendingChallenge, getPendingAnswers, submitHumanResponse } from '../engine/human-responses.js'
@@ -233,7 +233,7 @@ fightsRouter.post('/matchmake/:botId', botRateLimit(10_000), async (c) => {
   }
 
   if (isInFight(botId)) {
-    return c.json({ error: 'Bot is already in a fight.' }, 400)
+    return c.json({ error: 'Bot is already in a fight.', fightId: getActiveFightId(botId) }, 409)
   }
 
   const allBots = await db.select()
@@ -285,7 +285,7 @@ fightsRouter.post('/practice/:botId', botRateLimit(10_000), async (c) => {
   const bot = botRows[0]
 
   if (isInFight(botId)) {
-    return c.json({ error: 'Bot is already in a fight.' }, 400)
+    return c.json({ error: 'Bot is already in a fight.', fightId: getActiveFightId(botId) }, 409)
   }
 
   // Find all classic bots

server/src/routes/queue.ts

@@ -31,9 +31,10 @@ queueRouter.post('/join/:botId', async (c) => {
   try {
     const fightId = await joinQueue(botId)
     return c.json({ fightId, message: 'Matched! Fight starting.' })
-  } catch (err) {
+  } catch (err: any) {
     const message = err instanceof Error ? err.message : 'Queue error'
-    return c.json({ error: message }, 500)
+    const status = message.includes('already in a fight') ? 409 : 500
+    return c.json({ error: message, fightId: err?.fightId || undefined }, status)
   }
 })