fix(core): TRAC-281 Prevent breadcrumb array mutation on cached web pages

`.reverse()` was called directly on the breadcrumbs array returned from
React's `cache()`, mutating the shared reference. When `generateMetadata`
and `getWebPageBreadcrumbs` raced during render, the cached array could
be in reversed order, causing parent breadcrumb entries to disappear.

Also fix off-by-one in `truncateBreadcrumbs` where arrays exactly at the
target length were incorrectly truncated, replacing the middle item with
an ellipsis.

Fixes TRAC-281
Co-Authored-By: Claude <noreply@anthropic.com>

Author: chanceaclark

core/app/[locale]/(default)/webpages/[id]/contact/page.tsx

@@ -66,7 +66,7 @@ async function getWebPageBreadcrumbs(id: string): Promise<Breadcrumb[]> {
   const t = await getTranslations('WebPages.ContactUs');
 
   const webpage = await getWebPage(id);
-  const [, ...rest] = webpage.breadcrumbs.reverse();
+  const [, ...rest] = [...webpage.breadcrumbs].reverse();
   const breadcrumbs = [
     {
       label: t('home'),

core/app/[locale]/(default)/webpages/[id]/normal/page.tsx

@@ -41,7 +41,7 @@ async function getWebPageBreadcrumbs(id: string): Promise<Breadcrumb[]> {
   const t = await getTranslations('WebPages.Normal');
 
   const webpage = await getWebPage(id);
-  const [, ...rest] = webpage.breadcrumbs.reverse();
+  const [, ...rest] = [...webpage.breadcrumbs].reverse();
   const breadcrumbs = [
     {
       label: t('home'),

core/data-transformers/breadcrumbs-transformer.ts

@@ -22,7 +22,7 @@ export const breadcrumbsTransformer = (breadcrumbs: BreadcrumbsResult['breadcrum
 };
 
 export function truncateBreadcrumbs(breadcrumbs: Breadcrumb[], length: number): Breadcrumb[] {
-  if (breadcrumbs.length < length) {
+  if (breadcrumbs.length <= length) {
     return breadcrumbs;
   }