fix: ui fixes in transcript listing for books

lib/book-reference.ts

@@ -28,6 +28,20 @@ export function bookTitle(code: string): string {
   return b ? b.title : "";
 }
 
+/**
+ * Extract the (starting) verse number from a reference, for ordering lectures
+ * within a chapter. The verse is the last dotted numeric component, and for a
+ * range we take the start: "BG 2.13" → 13, "SB 1.2.3" → 3, "SB 3.27.11–16" →
+ * 11, "CC Madhya-līlā 20.101" → 101, "ISO Mantra 4" → 4. References with no
+ * number (e.g. bare "NOD") sort last (stable → keep their incoming order).
+ */
+export function parseVerse(reference: string | null): number {
+  const m = (reference ?? "").trim().match(/(\d+(?:\.\d+)*)/);
+  if (!m) return Number.MAX_SAFE_INTEGER;
+  const parts = m[1].split(".");
+  return Number(parts[parts.length - 1]);
+}
+
 /** A section is a canto (SB) or līlā (CC); null for books without that level. */
 export type ChapterSection = {
   key: string;