Insertion sort challenge

Editor assessment

The subject names the insertion sort challenge and nothing else: no verb, no symptom, no indication of what was wrong or what was fixed. A reader must open the diff to learn the substance, which is precisely the failure mode the subject-clarity dimension penalizes, though the words themselves are not gibberish. The fix type and curriculum scope are accurate. No body exists, and this is a change that needed one sentence of explanation. The PR reference is well formed. Understandable only as a pointer to a challenge, with no communication of content, so the message sits at mediocre rather than good.