Rename src to avatarUrl in collaborator

Editor assessment

The subject intends to say the src field was renamed to avatarUrl in the collaborator object, but doubled spaces where backticked names should be leave the sentence stuttering, and the body repeats the same broken phrasing. The fix type and absent scope are tolerable. One later bullet adds real content — a fallback to initials when the image fails — which is genuinely useful. The PR reference is well-formed. Understandable with effort, but the mangled identifier formatting in both headline and body keeps this at the acceptable tier.