fix(models): clear form state when loading model data for edit

Reset model selection, search query, and expanded provider state
when switching to edit mode to prevent stale UI state carrying over
from previous operations. Also ensure tieredPricing is properly set
or reset based on model data.

frontend/src/features/models/components/GlobalModelFormDialog.vue

@@ -604,6 +604,11 @@ function resetForm() {
 // 加载模型数据（编辑模式）
 function loadModelData() {
   if (!props.model) return
+  // 先重置创建模式的残留状态
+  selectedModel.value = null
+  searchQuery.value = ''
+  expandedProvider.value = null
+
   form.value = {
     name: props.model.name,
     display_name: props.model.display_name,
@@ -612,9 +617,10 @@ function loadModelData() {
     config: props.model.config ? { ...props.model.config } : { streaming: true },
     is_active: props.model.is_active,
   }
-  if (props.model.default_tiered_pricing) {
-    tieredPricing.value = JSON.parse(JSON.stringify(props.model.default_tiered_pricing))
-  }
+  // 确保 tieredPricing 也被正确设置或重置
+  tieredPricing.value = props.model.default_tiered_pricing
+    ? JSON.parse(JSON.stringify(props.model.default_tiered_pricing))
+    : null
 }
 
 // 使用 useFormDialog 统一处理对话框逻辑