fix: corregir estructura de columnas para UTable usando accessorKey en lugar de key

nuxt4-app/app/pages/explorer.vue

@@ -263,9 +263,13 @@ const displayColumns = computed(() => {
   const filtered = tableColumns.value
     .filter(col => visibleColumns.value.includes(col.key))
     .map(col => ({
-      key: col.key,
+      accessorKey: col.key,
-      label: col.label,
+      header: col.label,
-      sortable: true
+      cell: ({ row }: any) => {
+        const value = row.getValue(col.key)
+        if (value === null || value === undefined) return '-'
+        return String(value)
+      }
     }))
   console.log('📊 displayColumns computed:', filtered.length, 'visible columns')
   return filtered