fix(ui): проверять контекст расчёта OSPF оптимизатора

components/data-grids/route-optimizer-ospf-preview-data-grid.tsx

@@ -118,9 +118,9 @@ function RouteOptimizerOspfPreviewDataGrid({
     getRowId: (row) => row.id,
   })
 
-  if (error) {
+  if (error && rows.length === 0) {
     return (
-      <p className="px-3 py-2 text-xs text-destructive">Ошибка preview: {error}</p>
+      <p role="alert" className="px-3 py-2 text-xs text-destructive">Ошибка preview: {error}</p>
     )
   }
 
@@ -135,14 +135,18 @@ function RouteOptimizerOspfPreviewDataGrid({
   }
 
   return (
+    <>
+    {error && <p role="alert" className="px-3 py-2 text-xs text-warning">Ошибка preview: {error}. Последний снимок; актуальность неизвестна.</p>}
+    {loading && rows.length > 0 && <p role="status" className="px-3 py-2 text-xs text-muted-foreground">Обновление preview OSPF…</p>}
     <DataGridShell
       table={table}
       recordCount={rows.length}
-      isLoading={loading}
+      isLoading={loading && rows.length === 0}
       loadingMode="skeleton"
       tableClassNames={{ headerRow: "border-b bg-muted/30", bodyRow: "group/row" }}
       tableLayout={{ dense: true }}
     />
+    </>
   )
 }