Seed relay: dead NNTP connections found in 90 s and retried

Five ranges "never answered" in 10 minutes, yet their chunk came back in
0.3 s on a fresh connection: the news server drops idle connections
without telling, and the pool's next request on one waited for the
10-minute inactivity timeout. Now: SEED_NNTP_TIMEOUT_MS 90 s (inactivity;
slow ranges keep streaming), one retry on a fresh connection, and pooled
connections idle over 60 s are replaced before use.

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

config/indexer.ts

@@ -66,8 +66,12 @@ export default {
   seed: {
     /** NNTP connections the seed API fetches with for relay nodes (CONCEPT.md D38); 0: relay off. */
     nntpConnections: env.get('SEED_NNTP_CONNECTIONS', 0),
-    /** A relay XOVER may take this long: some old ranges come at ~1k headers/s (and slower when cold). */
-    nntpTimeoutMs: env.get('SEED_NNTP_TIMEOUT_MS', 10 * 60 * 1000),
+    /**
+     * Silence that counts as a dead connection during a relay XOVER (an
+     * inactivity timeout: slow ranges keep sending). Chunks that "never
+     * answered" in 10 minutes came in 0.3 s on a fresh connection.
+     */
+    nntpTimeoutMs: env.get('SEED_NNTP_TIMEOUT_MS', 90 * 1000),
   },
 
   backfill: {