feat: three-layer scene loading (?scene > config.json > main.json)

src/App.vue

@@ -43,8 +43,25 @@ const { loadGame, start, resumeAutoSave, makeChoice, clickHotspot, startChapter,
   saveGame, loadGameFromSlot, refreshSaves, saveSystem, engine } =
   useGameEngine(() => [videoElA.value, videoElB.value])
 
+async function resolveScenePath(): Promise<string> {
+  const params = new URLSearchParams(location.search)
+  const queryScene = params.get('scene')
+  if (queryScene) return queryScene.startsWith('/') ? queryScene : '/' + queryScene
+
+  try {
+    const resp = await fetch('/scenes/config.json')
+    if (resp.ok) {
+      const config = await resp.json()
+      if (config.sceneFile) return '/scenes/' + config.sceneFile
+    }
+  } catch { /* config.json optional */ }
+
+  return '/scenes/main.json'
+}
+
 async function init() {
-  await loadGame('/scenes/demo.json')
+  const scenePath = await resolveScenePath()
+  await loadGame(scenePath)
   loading.value = false
   hasAutoSave.value = (await saveSystem.load(0)) !== null
 }