refactor: move list sep logic to handlers

app/lib/download.ts

@@ -16,6 +16,7 @@
  */
 export function downloadCsv(
   headers: string[] | null,
+  headerLabels: string[],
   data: Array<Record<string, any> | any[]>,
   filename = 'data.csv',
   delimiter = ',',
@@ -66,7 +67,7 @@ export function downloadCsv(
     return Object.values(row).map(escape).join(delimiter)
   })
 
-  const headerRow = _headers ? _headers.join(delimiter) : null
+  const headerRow = headerLabels ? headerLabels.join(delimiter) : _headers ? _headers.join(delimiter) : null
   const csvString = (addBOM ? '\uFEFF' : '') + [headerRow, ...rows].filter(Boolean).join('\r\n')
 
   const blob = new Blob([csvString], { type: 'text/csv;charset=utf-8;' })
@@ -95,6 +96,7 @@ export function downloadCsv(
  */
 export async function downloadXls(
   headers: string[] | null,
+  headerLabels: string[],
   data: Array<Record<string, any> | any[]>,
   filename = 'data.xlsx',
   sheetName = 'Sheet1',
@@ -136,8 +138,10 @@ export async function downloadXls(
     return Object.values(row)
   })
 
-  // Combine headers and rows for sheet
-  const sheetData = _headers ? [_headers, ...rows] : rows
+  // Combine headers/labels and rows for sheet
+  // If caller provided headerLabels (as display labels), prefer them.
+  const sheetHeader = headerLabels ? headerLabels : _headers ? _headers : null
+  const sheetData = sheetHeader ? [sheetHeader, ...rows] : rows
 
   // Create worksheet and workbook
   const ws = utils.aoa_to_sheet(sheetData)