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>

app/services/SeedFetchPool.ts

@@ -8,8 +8,12 @@ interface Slot {
   usedAt: number
 }
 
-/** A pooled connection unused this long is replaced: the news server may have dropped it. */
-const IDLE_MS = 2 * 60 * 1000
+/**
+ * A pooled connection unused this long is replaced: the news server drops
+ * idle connections without telling, and a request on one then hangs until
+ * the inactivity timeout (LOG.md 2026-10-05 (11)).
+ */
+const IDLE_MS = 60 * 1000
 
 /**
  * NNTP connections in the seed API for relay nodes (CONCEPT.md D38): the
@@ -26,7 +30,16 @@ class SeedFetchPool {
     return indexerConfig.seed.nntpConnections
   }
 
+  /** Retried once on a fresh connection: a failure is nearly always a dead connection, not the articles. */
   async fetch(group: string, from: number, to: number): Promise<Buffer> {
+    try {
+      return await this.fetchOnce(group, from, to)
+    } catch {
+      return this.fetchOnce(group, from, to)
+    }
+  }
+
+  private async fetchOnce(group: string, from: number, to: number): Promise<Buffer> {
     const slot = await this.acquire()
     let ok = false
     try {
@@ -42,6 +55,14 @@ class SeedFetchPool {
     }
   }
 
+  /** Closes the idle connections (tests, shutdown); busy ones close when released. */
+  closeIdle() {
+    for (const slot of this.idle.splice(0)) {
+      slot.client.close()
+      this.open--
+    }
+  }
+
   private async acquire(): Promise<Slot> {
     while (true) {
       const slot = this.idle.pop()