feat: remove AI toolbar button, show AI panel by default

editor/App.vue

@@ -112,9 +112,6 @@ onMounted(() => restoreOrLoad())
         <button @click="showPreview = !showPreview" :class="{ secondary: true, active: showPreview }">
           {{ showPreview ? '📐 图谱' : '🎬 预览' }}
         </button>
-        <button @click="store.showAIPanel = !store.showAIPanel" :class="{ secondary: true, active: store.showAIPanel }">
-          🤖 AI
-        </button>
       </div>
     </div>
 

editor/stores/editorStore.ts

@@ -25,7 +25,7 @@ export const useEditorStore = defineStore('editor', () => {
   const dirty = ref(false)
   const sourcePath = ref('/scenes/demo.json')
   const deepseekKey = ref(localStorage.getItem('deepseek_key') || '')
-  const showAIPanel = ref(false)
+  const showAIPanel = ref(true)
   const aiCollapsed = ref(true)
   const aiSessionId = ref('')
   const aiChanges = ref<AIDiff | null>(null)