Rebuild: drop NUL from batches; chunk deadline 180 s

A file name with a NUL ("…Brutal Erpresst.ra\u0000…") failed every
batch of range 155595 (HTTP 500, jsonb: \u0000 cannot be converted to
text), so the range looped. fromWire drops NUL from every string.

The chunk deadline was given up 258 times in 3 hours at 300 s (~1.4 a
minute, each holding a connection for 5 minutes): 180 s.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

config/coordinator.ts

@@ -41,9 +41,10 @@ export default {
    * A chunk still coming in after this long is given up (its connection
    * closed) and fetched again: a reply that trickles never goes quiet long
    * enough for nntpTimeoutMs, and kept a worker waiting on one chunk for an
-   * hour (LOG.md 2026-10-10 (2)). Chunks take 3–35 s.
+   * hour (LOG.md 2026-10-10 (2)). Chunks take 3–35 s; at 300 s, 258 were
+   * given up in 3 hours (~1.4 a minute, each holding a connection 5 minutes).
    */
-  nntpChunkDeadlineMs: env.get('NNTP_CHUNK_DEADLINE_SECONDS', 5 * 60) * 1000,
+  nntpChunkDeadlineMs: env.get('NNTP_CHUNK_DEADLINE_SECONDS', 3 * 60) * 1000,
   /**
    * A chunk not fetched after this long is asked again on another
    * connection; the first answer wins and the other connection is closed.