fix: server crash from syntax error in challenges.ts, voice overlap, human fight UX

- Remove stray duplicate template block outside TEMPLATES array that caused parse error preventing server startup (fixes /api/queue/status 500)
- Add choices field to Challenge/PromptEntry interfaces for multiple choice support
- Allow voice lines to overlap naturally instead of cancelling previous speech on every call, with safety flush at depth > 3
- Buffer challenges during cooldown in polling path, auto-submit random choice on timeout
- Block auto-battle for human fights, guard replay-done auto-transition

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

frontend/src/game/sounds.ts

@@ -265,25 +265,34 @@ if (typeof speechSynthesis !== 'undefined') {
   loadVoices()
 }
 
+let _speechQueueDepth = 0
+
 function speak(text: string, profileName: string, cancelPrevious: boolean = false, _echo: boolean = false) {
   if (typeof speechSynthesis === 'undefined') return
   if (masterMuted) return
   if (!voicesLoaded) loadVoices()
-  // Always cancel queued speech — only the most recent line matters
-  // This prevents stale voiceovers from playing seconds after their visual moment
-  speechSynthesis.cancel()
+  // Only flush if queue is getting deep — allows voices to overlap naturally
+  if (cancelPrevious || speechSynthesis.pending && speechSynthesis.speaking) {
+    // 2+ queued: drop the queue but let current utterance finish
+    const queued = _speechQueueDepth
+    if (queued > 3) speechSynthesis.cancel()
+  }
   const profile = voiceProfiles[profileName] || voiceProfiles.announcer
   const utter = new SpeechSynthesisUtterance(text)
   if (profile.voice) utter.voice = profile.voice
   utter.pitch = profile.pitch
   utter.rate = profile.rate
   utter.volume = profile.volume
+  _speechQueueDepth++
+  utter.onend = () => { _speechQueueDepth = Math.max(0, _speechQueueDepth - 1) }
+  utter.onerror = () => { _speechQueueDepth = Math.max(0, _speechQueueDepth - 1) }
   speechSynthesis.speak(utter)
 }
 
 export function stopAllAudio() {
   stopMusic()
   if (typeof speechSynthesis !== 'undefined') speechSynthesis.cancel()
+  _speechQueueDepth = 0
 }
 
 // Public voice functions
@@ -292,13 +301,15 @@ export function announce(text: string, pitch?: number, rate?: number) {
   if (pitch !== undefined || rate !== undefined) {
     if (typeof speechSynthesis === 'undefined') return
     if (!voicesLoaded) loadVoices()
-    speechSynthesis.cancel() // cancel previous to stay in sync with visuals
     const utter = new SpeechSynthesisUtterance(text)
     const profile = voiceProfiles.announcer
     if (profile.voice) utter.voice = profile.voice
     utter.pitch = pitch ?? 1.0
     utter.rate = rate ?? 0.8
     utter.volume = 1.0
+    _speechQueueDepth++
+    utter.onend = () => { _speechQueueDepth = Math.max(0, _speechQueueDepth - 1) }
+    utter.onerror = () => { _speechQueueDepth = Math.max(0, _speechQueueDepth - 1) }
     speechSynthesis.speak(utter)
   } else {
     speak(text, 'announcer')