Rebuild: 2-minute NNTP reply timeout; the Rust worker runs on homelab

Eweka stopped answering on all 40 of the coordinator's long-lived
connections (quiet sockets; a fresh connection fetched the same chunk in
20 s): with a 10-minute timeout the prefetcher fetched one chunk a
minute. The timeout (silence, not duration) is 2 minutes now: 365-411k
articles/s after the restart. tools/probe_chunk.ts times a chunk
compressed and plain.

README and REBUILD.md: edge-node, the Rust worker, is the one running
(8x less CPU per header, 20x less memory than edge:node in production).

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

config/coordinator.ts

@@ -30,8 +30,13 @@ export default {
   leaseTtlSeconds: env.get('LEASE_TTL_SECONDS', 15 * 60),
   /** NNTP connections the coordinator fetches headers with. */
   nntpConnections: env.get('NNTP_CONNECTIONS', 4),
-  /** A reply with no data for this long fails (old ranges answer slowly). */
-  nntpTimeoutMs: env.get('NNTP_TIMEOUT_MS', 10 * 60 * 1000),
+  /**
+   * A reply with no data for this long fails, and its connection is replaced.
+   * Eweka sometimes stops answering on long-lived connections (all 40 quiet,
+   * a fresh one answers in seconds; LOG.md 2026-10-09 (14)): at 10 minutes
+   * the prefetcher nearly stopped. Data arrives within seconds otherwise.
+   */
+  nntpTimeoutMs: env.get('NNTP_TIMEOUT_MS', 2 * 60 * 1000),
   spool: {
     dir: env.get('SPOOL_DIR', app.tmpPath('spool')),
     /** Ranges kept fetched ahead, per active lease. */