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>

tools/probe_chunk.ts

@@ -0,0 +1,26 @@
+/**
+ * One XOVER chunk fetched compressed (with a reply timeout) and plain, timed:
+ * whether a chunk that never finishes compressed is whole without compression.
+ *
+ *   node --env-file=.env --import=@poppinss/ts-exec tools/probe_chunk.ts <group> <from> <to> [timeoutSeconds]
+ */
+import { unzipSync } from 'node:zlib'
+import { XoverClient } from '#lib/nntp/index'
+
+const [group, from, to, timeout] = process.argv.slice(2)
+const env = process.env
+const connect = (compress: boolean, timeoutMs: number) =>
+  XoverClient.connect({ host: env.NNTP_HOST!, port: Number(env.NNTP_PORT ?? 563), user: env.NNTP_USER, password: env.NNTP_PASSWORD, secure: (env.NNTP_SECURE ?? 'true') !== 'false', compress, timeoutMs })
+for (const compress of [true, false]) {
+  const c = await connect(compress, Number(timeout ?? 90) * 1000)
+  await c.group(group)
+  const at = Date.now()
+  try {
+    const raw = await c.xoverRaw(Number(from), Number(to))
+    const lines = unzipSync(raw).toString().split('\r\n').filter((l) => l.includes('\t')).length
+    console.log(`${compress ? 'compressed' : 'plain'}: ${raw.length} bytes, ${lines} lines in ${((Date.now() - at) / 1000).toFixed(1)} s`)
+  } catch (e: any) {
+    console.log(`${compress ? 'compressed' : 'plain'}: ${e.message} after ${((Date.now() - at) / 1000).toFixed(1)} s`)
+  }
+  c.close()
+}