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/engine/human-responses.ts

@@ -0,0 +1,100 @@
+// In-memory store for pending human challenges.
+// When the fight engine needs a human's response, it stores the challenge here
+// and waits for the browser to submit the answer via REST.
+
+import type { Challenge } from './challenges.js'
+
+interface PendingChallenge {
+  fightId: string
+  botId: string
+  challenge: Challenge
+  roundNumber: number
+  createdAt: number
+  resolve: (response: { answer: string; trashTalk?: string }) => void
+  timeoutHandle: ReturnType<typeof setTimeout>
+}
+
+const pending = new Map<string, PendingChallenge>()
+
+const HUMAN_TIMEOUT_MS = 8_000
+
+export function isHumanPlayer(webhookUrl: string): boolean {
+  return webhookUrl === 'http://human.local/'
+}
+
+export function waitForHumanResponse(
+  fightId: string,
+  botId: string,
+  challenge: Challenge,
+  roundNumber: number,
+): Promise<{ answer: string | null; trashTalk?: string; timedOut: boolean }> {
+  return new Promise((resolve) => {
+    const key = `${fightId}:${botId}`
+
+    const timeoutHandle = setTimeout(() => {
+      pending.delete(key)
+      console.log(`[human] ${key} timed out after ${HUMAN_TIMEOUT_MS}ms`)
+      resolve({ answer: null, timedOut: true })
+    }, HUMAN_TIMEOUT_MS)
+
+    pending.set(key, {
+      fightId,
+      botId,
+      challenge,
+      roundNumber,
+      createdAt: Date.now(),
+      resolve: (response) => {
+        clearTimeout(timeoutHandle)
+        pending.delete(key)
+        resolve({ answer: response.answer, trashTalk: response.trashTalk, timedOut: false })
+      },
+      timeoutHandle,
+    })
+
+    console.log(`[human] waiting for response: ${key} round=${roundNumber} type=${challenge.type}`)
+  })
+}
+
+export function submitHumanResponse(
+  fightId: string,
+  botId: string,
+  answer: string,
+  trashTalk?: string,
+): boolean {
+  const key = `${fightId}:${botId}`
+  const entry = pending.get(key)
+  if (!entry) return false
+  console.log(`[human] response received: ${key} answer=${answer.slice(0, 80)}`)
+  entry.resolve({ answer: answer.slice(0, 2000), trashTalk: trashTalk?.slice(0, 200) })
+  return true
+}
+
+export function getPendingChallenge(
+  fightId: string,
+  botId: string,
+): {
+  type: string
+  label: string
+  prompt: string
+  roundNumber: number
+  timeoutMs: number
+  remainingMs: number
+  scoring: string
+} | null {
+  const key = `${fightId}:${botId}`
+  const entry = pending.get(key)
+  if (!entry) return null
+
+  const elapsed = Date.now() - entry.createdAt
+  const remaining = Math.max(0, HUMAN_TIMEOUT_MS - elapsed)
+
+  return {
+    type: entry.challenge.type,
+    label: entry.challenge.label,
+    prompt: entry.challenge.prompt,
+    roundNumber: entry.roundNumber,
+    timeoutMs: HUMAN_TIMEOUT_MS,
+    remainingMs: remaining,
+    scoring: entry.challenge.scoring,
+  }
+}