✨feature: First push to git

src/output/sheets.ts

@@ -0,0 +1,23 @@
+const invalidSheetCharacters = /[:/\\?*[\]]/g;
+
+export function sanitizeSheetName(input: string): string {
+  const cleaned = input.replace(invalidSheetCharacters, ' ').replace(/\s+/g, ' ').trim();
+  return (cleaned || 'Newsletter').slice(0, 100);
+}
+
+export function escapeCell(value: unknown): unknown {
+  if (typeof value !== 'string') {
+    return value;
+  }
+  return /^[=+\-@]/.test(value) ? `'${value}` : value;
+}
+
+export interface CatalogPayload {
+  rows: Record<string, unknown>[];
+  sponsors: Record<string, unknown>[];
+  deadLinks: Record<string, unknown>[];
+}
+
+export interface OutputWriter {
+  write(payload: CatalogPayload): Promise<unknown>;
+}