a.b.0day.stuffz sends steadily but slowly (~400 kB a minute, 5-7 minutes per 100k chunk): the fixed deadline (90 s, doubling up to 360 s) gave its chunks up again and again, and two of its ranges' worker streams timed out. A stall is a request that got less than NNTP_STALL_KB_PER_MINUTE (100) in the last minute (the stuck replies got ~25 kB a minute); then its connection is closed and the chunk fetched again. Replaces NNTP_CHUNK_DEADLINE_SECONDS. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>