feat: human vs AI mode — live typing challenges, baby growth system, SSE rounds

- Add choose-mode step: "I BUILD BOTS" vs "I FIGHT MYSELF" paths
- Human registration with baby avatar picker, no webhook required
- Live fight scene with SSE round streaming and real-time challenge UI
- 5-second timer per round, submit answers via browser
- Baby → toddler → kid → teen → adult → hero → super growth stages
- Huge sparkly baby eyes, diapers, pacifiers, bibs, rattles, rosy cheeks
- Speech bubble positioning fix (pushed to outside of sprite)
- Canvas text rendering via offscreen canvas to bypass kaplay color issues
- Voice timing improvements: await pauses between voice lines and hits
- 30 devastating announcement lines, 15 critical/hit word variants
- Orchestrator human player detection + waitForHumanResponse system
- Server endpoints: GET /challenge/:botId, POST /respond/:botId
- Human player auth: register-human route, isHuman flag on login

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

server/src/routes/fights.ts

@@ -8,6 +8,7 @@ import { startFightLoop } from '../engine/fight-loop.js'
 import { runFight, runFightAsync, isInFight } from '../engine/orchestrator.js'
 import { fightEvents } from '../engine/events.js'
 import { botRateLimit } from '../middleware/rate-limit.js'
+import { getPendingChallenge, submitHumanResponse } from '../engine/human-responses.js'
 
 export const fightsRouter = new Hono()
 
@@ -221,6 +222,45 @@ fightsRouter.post('/matchmake/:botId', botRateLimit(10_000), async (c) => {
   })
 })
 
+// Get pending challenge for a human player in an active fight
+fightsRouter.get('/:fightId/challenge/:botId', async (c) => {
+  const fightId = c.req.param('fightId')
+  const botId = c.req.param('botId')
+
+  const challenge = getPendingChallenge(fightId, botId)
+  if (!challenge) {
+    // Check if fight is still active
+    const fight = await db.select({ status: schema.fights.status })
+      .from(schema.fights)
+      .where(eq(schema.fights.id, fightId))
+      .limit(1)
+
+    const status = fight[0]?.status || 'unknown'
+    return c.json({ pending: false, fightStatus: status })
+  }
+
+  return c.json({ pending: true, ...challenge })
+})
+
+// Submit human response to a challenge
+fightsRouter.post('/:fightId/respond/:botId', async (c) => {
+  const fightId = c.req.param('fightId')
+  const botId = c.req.param('botId')
+  const body = await c.req.json()
+
+  const { answer, trashTalk } = body
+  if (!answer || typeof answer !== 'string') {
+    return c.json({ error: 'Answer is required.' }, 400)
+  }
+
+  const accepted = submitHumanResponse(fightId, botId, answer, trashTalk)
+  if (!accepted) {
+    return c.json({ error: 'No pending challenge found. May have timed out.' }, 404)
+  }
+
+  return c.json({ accepted: true })
+})
+
 // SSE stream for live fight events
 fightsRouter.get('/:id/stream', (c) => {
   const fightId = c.req.param('id')