fix: update BOM operations when routing is changed

The routing field handler only fetched operations from the routing when
the operations table was empty. When a new BOM version is created (via
"New Version"), operations are copied from the source BOM, so selecting a
different routing left the old operations in place - both in the form and
after saving.

Drop the `!frm.doc.operations.length` guard from the routing handler so
that (re)selecting a routing always refetches the operations from that
routing via the existing get_routing method, which clears and repopulates
the operations table.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
(cherry picked from commit 758a837de4)

erpnext/manufacturing/doctype/bom/bom.js

@@ -441,7 +441,11 @@ frappe.ui.form.on("BOM", {
 	},
 
 	routing(frm) {
-		if (frm.doc.routing && frm.doc.with_operations && !frm.doc.operations.length) {
+		// Refetch operations whenever the routing is (re)selected, so that
+		// changing the routing - e.g. on a new BOM version copied from another
+		// BOM - replaces the operations with those of the newly selected routing
+		// instead of keeping the old ones.
+		if (frm.doc.routing && frm.doc.with_operations) {
 			frappe.call({
 				doc: frm.doc,
 				method: "get_routing",