fix: wait for DOM update before attaching video element

src/App.vue

@@ -1,5 +1,5 @@
 <script setup lang="ts">
-import { ref } from 'vue'
+import { ref, nextTick } from 'vue'
 import GamePlayer from '@/components/GamePlayer.vue'
 import ChoicePanel from '@/components/ChoicePanel.vue'
 import { useGameEngine } from '@/composables/useGameEngine'
@@ -14,6 +14,7 @@ const { loadGame, start, makeChoice } = useGameEngine(() => videoElRef.value)
 async function init() {
   await loadGame('/scenes/demo.json')
   loading.value = false
+  await nextTick()
   start()
 }