Rebuild: hedged chunk fetches and connection max age (both off by default)

A chunk not in after NNTP_HEDGE_AFTER_SECONDS (10) is asked again on one
of NNTP_HEDGE_CONNECTIONS spare connections; the first answer wins and
the other connection is closed (lib/nntp/hedge.ts, tested). Connections
can be retired after NNTP_CONNECTION_MAX_MINUTES (±25%). The prefetch
report counts hedges and slow first requests by connection age.

Homelab, 15 min each: hedging on (40 + 6) 280k articles/s, off 273k.
The second request won about half of its races, but ~25-35% of first
requests were slow (>10 s) at every connection age, so neither helps:
Eweka is slow under our load, not on particular connections. Both
off by default; the age statistics stay.

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

config/coordinator.ts

@@ -37,6 +37,24 @@ export default {
    * the prefetcher nearly stopped. Data arrives within seconds otherwise.
    */
   nntpTimeoutMs: env.get('NNTP_TIMEOUT_MS', 2 * 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.
+   * Eweka stalls single requests: the same chunk took 27–52 s on one
+   * connection and 1–9 s on another at the same moment; median ~3 s
+   * (LOG.md 2026-10-09 (15)). Measured in production (40 + 6 connections vs
+   * 40, 15 min each): 280k vs 273k articles/s, within the noise; the second
+   * request won half the time. Off by default.
+   */
+  nntpHedgeAfterMs: env.get('NNTP_HEDGE_AFTER_SECONDS', 10) * 1000,
+  /** Of nntpConnections, kept for those second requests (the prefetcher's loops are the rest). 0: no hedging. */
+  nntpHedgeConnections: env.get('NNTP_HEDGE_CONNECTIONS', 0),
+  /**
+   * A connection is closed after this long (when it's free), and a fresh one
+   * opened. 0: never. Requests were as often slow (>10 s) on connections
+   * under 2 minutes old as on ones over 10 (~25–35%; LOG.md 2026-10-09 (16)).
+   */
+  nntpConnectionMaxMs: env.get('NNTP_CONNECTION_MAX_MINUTES', 0) * 60 * 1000,
   spool: {
     dir: env.get('SPOOL_DIR', app.tmpPath('spool')),
     /** Ranges kept fetched ahead, per active lease. */