A PR more than 100 commits ahead of its merge-base paginates the compare
endpoint; pages after the first carry files: null, so the bare .files[]
made jq die with 'cannot iterate over: null' on every retry and forced
the classifier's fail-open path (all lanes on, ci_review gate demanding
a label with zero CI-sensitive files in the diff). .files[]? keeps the
page-one file list and ignores the null tail.
21f971bbab