Update challengePlayer URL key in URLs data structure to use 'link.challenge.main' for improved navigation consistency.

src/__data__/urls.ts

@@ -40,6 +40,6 @@ export const URLs = {
   submissionDetailsPath: makeUrl('/submissions/:userId/:submissionId'),
   
   // External links
-  challengePlayer: navs['link.challenge'] || '/challenge',
+  challengePlayer: navs['link.challenge.main'] || '/challenge',
 }