When attempt1 delivers data but fails structured reporting, the final
attempt fast-exits all_seen with 0 articles — the record then showed
nothing delivered, leaving the operator to guess. After the attempt loop,
merge earlier attempts' delivered articles (URL-deduped, archive_path
required) into the final envelope, recompute counts, and record each
attempt's contribution in warnings. Single verdict, full visibility.
Unit-tested: 0+3+2(1 dup) → 4 articles, per-attempt notes.