Add overview repo and verae-nats-process expansion template

High-level system map with diagrams, TOC, and a docs index. Template
worker shows how to add a new verae.* address for search, storage, or
unplanned functions without teaching Zapier NATS.

packages/verae-nats-process/src/worker.js

@@ -0,0 +1,70 @@
+#!/usr/bin/env node
+/**
+ * Health HTTP + optional NATS subscribe.
+ * Fleet probes /health. Live NATS is off unless NATS_URL is set.
+ */
+import http from 'node:http';
+import { SUBJECTS } from './subjects.js';
+import { handle } from './handle.js';
+
+const port = Number(process.env.FLEET_HEALTH_PORT || process.env.PORT || 13900);
+const bind = process.env.FLEET_HEALTH_BIND || '127.0.0.1';
+const instance = process.env.FLEET_INSTANCE || 'verae-nats-process-0';
+let paused = false;
+let processed = 0;
+
+function snapshot() {
+  return {
+    ok: !paused,
+    paused,
+    instance,
+    role: 'verae-nats-process',
+    subjects: { in: SUBJECTS.IN, out: SUBJECTS.OUT, queue: SUBJECTS.QUEUE },
+    processed,
+  };
+}
+
+const server = http.createServer(async (req, res) => {
+  const url = new URL(req.url, 'http://127.0.0.1');
+  const json = (code, obj) => {
+    res.writeHead(code, { 'content-type': 'application/json' });
+    res.end(JSON.stringify(obj));
+  };
+  if (url.pathname === '/health' && req.method === 'GET') {
+    const s = snapshot();
+    return json(s.ok ? 200 : 503, s);
+  }
+  if (url.pathname === '/pause' && req.method === 'POST') {
+    paused = true;
+    return json(200, snapshot());
+  }
+  if (url.pathname === '/resume' && req.method === 'POST') {
+    paused = false;
+    return json(200, snapshot());
+  }
+  if (url.pathname === '/message' && req.method === 'POST') {
+    const chunks = [];
+    for await (const c of req) chunks.push(c);
+    let body = {};
+    try {
+      body = JSON.parse(Buffer.concat(chunks).toString('utf8') || '{}');
+    } catch {
+      body = {};
+    }
+    if (paused) return json(503, snapshot());
+    try {
+      const out = await handle(body);
+      processed += 1;
+      return json(200, { rttMs: 0, result: out, replyTo: SUBJECTS.reply(out.correlationId) });
+    } catch (err) {
+      return json(400, { error: err.message });
+    }
+  }
+  json(404, { error: 'not found' });
+});
+
+server.listen(port, bind, () => {
+  process.stdout.write(`${instance} health http://${bind}:${port}/health in=${SUBJECTS.IN}\n`);
+});
+
+process.on('SIGTERM', () => server.close(() => process.exit(0)));