fix(aihr): polish model fallback wording

frontend/src/views/system/model/index.vue

@@ -253,7 +253,7 @@
           </el-select>
         </el-form-item>
         <el-form-item label="用途">
-          <el-input v-model="modelForm.modelDescribe" placeholder="用于 Demo 对话与 RAG 生成" />
+          <el-input v-model="modelForm.modelDescribe" placeholder="用于通用对话与 RAG 生成" />
         </el-form-item>
         <el-form-item label="维度">
           <el-input-number v-model="modelForm.modelDimension" :min="0" :controls="false" placeholder="向量模型填写" />
@@ -445,7 +445,7 @@ const seedModels: ModelConfig[] = [
     category: 'chat',
     modelName: 'deepseek-chat',
     providerCode: 'deepseek',
-    modelDescribe: '用于 Demo 对话与 RAG 生成',
+    modelDescribe: '用于通用对话与 RAG 生成',
     modelShow: 'Y',
     apiHost: '',
     enabled: true,