Add exhaustive NATS factorial, MQTT/UDP probes, and optimal-config report.

Compares r=1 vs r=3, file vs memory, reconnect tax, and projects three
HP DL360 Gen10 NVMe + 10GbE boxes. Keep NATS; do not switch to MQTT/UDP.

packages/verae-nats-cluster/scripts/latency.mjs

@@ -1,9 +1,10 @@
 #!/usr/bin/env node
 /**
  * Pub→sub round trip through the cluster (two connections).
- * Usage: NATS_URL=... node latency.mjs [count] [payloadBytes] [publishers] [ping|flood]
- * ping  = sequential publish-wait (one-message RTT)
- * flood = publish the batch then drain (queueing under burst)
+ * Usage: NATS_URL=... node latency.mjs [count] [payloadBytes] [publishers] [ping|flood|reconnect]
+ * ping       = sequential publish-wait on persistent sockets (one-message RTT)
+ * flood      = publish the batch then drain (queueing under burst)
+ * reconnect  = connect, one publish, wait, close — measures handshake tax
  */
 import { connect, headers } from "nats";
 
@@ -23,7 +24,33 @@ function pct(sorted, p) {
 }
 
 const samples = [];
-if (mode === "ping") {
+if (mode === "reconnect") {
+  const subNc = await connect({ servers, name: "lat-sub" });
+  let resolveOne = null;
+  const sub = subNc.subscribe(subject, { max: count });
+  const consume = (async () => {
+    for await (const m of sub) {
+      const sent = Number(m.headers?.get("t") || 0);
+      samples.push(Number(process.hrtime.bigint() / 1000n) - sent);
+      resolveOne?.();
+    }
+  })();
+  await subNc.flush();
+  for (let i = 0; i < count; i++) {
+    const got = new Promise((r) => {
+      resolveOne = r;
+    });
+    const pubNc = await connect({ servers, name: `lat-re-${i}` });
+    const h = headers();
+    h.set("t", String(process.hrtime.bigint() / 1000n));
+    pubNc.publish(subject, payload, { headers: h });
+    await pubNc.flush();
+    await got;
+    await pubNc.close();
+  }
+  await consume;
+  await subNc.close();
+} else if (mode === "ping") {
   const subNc = await connect({ servers, name: "lat-sub" });
   const pubNc = await connect({ servers, name: "lat-pub" });
   let resolveOne = null;