fix: prevent FightViewer random resets from concurrent kaplay init

- Guard initScene() with initializingScene flag to prevent concurrent calls
- Don't auto-reinit scene on WebGL context restore during active replay
- Block initScene() after component is destroyed
- Static audio files now play even before Kokoro worker loads
- kokoroSpeak/kokoroSpeakAsync check cache before requiring worker ready

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

frontend/src/components/FightViewer.vue

@@ -28,6 +28,7 @@ let scene: FightSceneController | null = null
 const sceneReady = ref(false)
 let cleanupTimerHandle: ReturnType<typeof setTimeout> | null = null
 let destroyed = false
+let initializingScene = false
 const contextLost = ref(false)
 
 const isReplaying = ref(false)
@@ -174,6 +175,8 @@ onUnmounted(() => {
 
 async function initScene() {
   if (!props.fight.botA || !props.fight.botB) return
+  if (initializingScene || destroyed) return // prevent concurrent init or post-destroy init
+  initializingScene = true
   // Destroy previous scene fully
   sceneReady.value = false
   if (scene) { scene.destroy(); scene = null }
@@ -207,8 +210,10 @@ async function initScene() {
     sceneReady.value = false
   })
   newCanvas.addEventListener('webglcontextrestored', () => {
+    // Don't auto-reinit during replay — just mark context as restored
+    // The contextLost overlay will let users tap to reload if needed
     contextLost.value = false
-    initScene() // Re-create the scene with fresh context
+    if (!isReplaying.value) initScene()
   })
 
   // Wrap scene creation in try/catch + timeout so a mobile sprite loading failure
@@ -230,6 +235,8 @@ async function initScene() {
     }
   } catch (err) {
     console.error('[FightViewer] Scene creation failed — continuing without canvas:', err)
+  } finally {
+    initializingScene = false
   }
 }