feat: collapsible AI panel with overlay layout

editor/App.vue

@@ -143,9 +143,10 @@ onMounted(() => restoreOrLoad())
         @delete-scene="delNode"
         @close="store.selectedNodeId = null"
       />
-      <AIPanel v-if="store.showAIPanel" />
     </div>
 
+    <AIPanel v-if="store.showAIPanel" />
+
     <input ref="fileInputRef" type="file" accept=".json" style="display:none" @change="onFileSelected" />
   </div>
 </template>
@@ -158,7 +159,7 @@ html, body { width: 100%; height: 100%; overflow: hidden; background: #0a0a16; c
 </style>
 
 <style scoped>
-.editor-layout { width: 100%; height: 100%; display: flex; flex-direction: column; }
+.editor-layout { width: 100%; height: 100%; display: flex; flex-direction: column; position: relative; }
 .toolbar { display: flex; align-items: center; gap: 12px; padding: 10px 16px; background: #111122; border-bottom: 1px solid rgba(255,255,255,0.06); flex-shrink: 0; }
 .toolbar-title { font-size: 15px; font-weight: 600; color: #ddd; letter-spacing: 1px; margin-right: 16px; }
 .toolbar-actions { display: flex; gap: 8px; }