Function scan_commit_body 

pub async fn scan_commit_body(cwd: &Path, sha: &str) -> String

Fetch a commit’s message body - everything after the subject line, with the trailing newline trimmed. Empty for a subject-only commit. Kept out of scan_commits because a multi-line body would break its line-per-commit git log parse; the stepper fetches it lazily per commit alongside the hunks.