feat(frontend): listExportableParams enumerates export options

frontend/src/lib/dataExport.js

@@ -21,3 +21,35 @@ export function extractValue(status, param) {
       return null;
   }
 }
+
+// Build the grouped, ordered list of exportable parameters.
+// Session metrics (total, success_rate, then each dynamic count category found
+// in the data) come first; then every field defined in the daily template,
+// including inactive ones (historical data may exist).
+export function listExportableParams(dailyTemplate, statuses) {
+  const params = [
+    { id: '__total__', label: 'Total attempts', group: 'metrics', kind: 'total' },
+    { id: '__success_rate__', label: 'Success rate', group: 'metrics', kind: 'success_rate' },
+  ];
+
+  const cats = new Set();
+  for (const s of statuses ?? []) {
+    const counts = s?.analysis_summary?.counts;
+    if (counts && typeof counts === 'object') {
+      for (const k of Object.keys(counts)) cats.add(k);
+    }
+  }
+  for (const cat of [...cats].sort()) {
+    params.push({ id: `__cat__${cat}`, label: cat, group: 'metrics', kind: 'category', category: cat });
+  }
+
+  for (const f of dailyTemplate ?? []) {
+    if (f.builtin) {
+      params.push({ id: `b:${f.fieldId}`, label: f.label, group: 'daily', kind: 'builtin', statusKey: f.key });
+    } else {
+      params.push({ id: `c:${f.fieldId}`, label: f.label, group: 'daily', kind: 'custom', fieldId: f.fieldId });
+    }
+  }
+
+  return params;
+}