fix(merge): page labels, retain-labels option, and workflow alignment with cpdf

src/js/logic/alternate-merge-page.ts

@@ -174,7 +174,12 @@ async function mixPages() {
       return;
     }
 
-    const mergedBytes = await interleavePdfs(filesToMerge);
+    const retainCheckbox = document.getElementById(
+      'retain-page-labels'
+    ) as HTMLInputElement | null;
+    const mergedBytes = await interleavePdfs(filesToMerge, {
+      retainPageLabels: retainCheckbox?.checked ?? false,
+    });
     hideLoader();
     const blob = new Blob([new Uint8Array(mergedBytes)], {
       type: 'application/pdf',

src/js/logic/merge-pdf-page.ts

@@ -385,11 +385,16 @@ export async function merge() {
       }
     }
 
+    const retainCheckbox = document.getElementById(
+      'retain-page-labels'
+    ) as HTMLInputElement | null;
+
     const message: MergeMessage = {
       command: 'merge',
       files: filesToMerge,
       jobs: jobs,
       cpdfUrl: WasmProvider.getUrl('cpdf')! + 'coherentpdf.browser.min.js',
+      retainPageLabels: retainCheckbox?.checked ?? false,
     };
 
     mergeWorker.postMessage(

src/js/logic/pdf-workflow-page.ts

@@ -1286,6 +1286,7 @@ function showNodeSettings(node: BaseWorkflowNode) {
     'subsetFonts',
     'convertToGrayscale',
     'removeThumbnails',
+    'retainPageLabels',
   ]);
   const multiSelectDropdowns = new Set(['language']);
   const advancedControls = new Set(['resolution', 'binarize', 'whitelist']);
@@ -1307,6 +1308,8 @@ function showNodeSettings(node: BaseWorkflowNode) {
     y0: 'Top edge in points',
     x1: 'Right edge in points',
     y1: 'Bottom edge in points',
+    retainPageLabels:
+      "Off (default): natural 1–N numbering. On: each file's original page labels are preserved (may produce duplicate labels).",
   };
 
   const inputClass =