Add runnable smoke-test clients for each SDK

Each package gets a small example program that exercises the real
client: with no ORIGIN_SERVICE_KEY set it runs against a local mock
check-in server, otherwise it checks in against ORIGIN_URL/Origin's
public endpoint. Wired into CI (mock mode) as a regression check, and
documented per README.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

js/examples/testclient.mjs

@@ -0,0 +1,103 @@
+// Runnable smoke test for the JS/TS originclient SDK.
+//
+// Without ORIGIN_SERVICE_KEY set, it spins up a local mock check-in server
+// and exercises the client against it — no network, no credentials needed.
+// With ORIGIN_SERVICE_KEY set, it performs a real check-in against
+// ORIGIN_URL (or Origin's public endpoint) so the SDK can be smoke-tested
+// end-to-end against a live server.
+//
+// Run `npm run build` first (this imports the compiled dist/ output).
+// Usage: node examples/testclient.mjs [--watch]
+
+import { createServer } from "node:http";
+import { OriginClient } from "../dist/index.js";
+
+function envOr(key, def) {
+  return process.env[key] || def;
+}
+
+async function startMockServer() {
+  return new Promise((resolve) => {
+    const server = createServer((req, res) => {
+      let raw = "";
+      req.on("data", (chunk) => {
+        raw += chunk;
+      });
+      req.on("end", () => {
+        const payload = JSON.parse(raw || "{}");
+        console.log(
+          `mock server received check-in: type=${payload.type} name=${payload.name} ` +
+            `install_id=${payload.unique_install_id} key=${req.headers["x-origin-service-key"]}`,
+        );
+        res.writeHead(200, { "Content-Type": "application/json" });
+        res.end(
+          JSON.stringify({
+            success: true,
+            service_instance_id: 1,
+            unique_install_id: payload.unique_install_id,
+            status: "provisioning",
+            pinged_at: "2026-08-01T00:00:00Z",
+          }),
+        );
+      });
+    });
+    server.listen(0, "127.0.0.1", () => {
+      const address = server.address();
+      resolve({ server, url: `http://127.0.0.1:${address.port}` });
+    });
+  });
+}
+
+async function main() {
+  const watch = process.argv.includes("--watch");
+
+  const config = {
+    url: process.env.ORIGIN_URL,
+    serviceKey: process.env.ORIGIN_SERVICE_KEY,
+    type: envOr("ORIGIN_TYPE", "icy2-testclient"),
+    version: envOr("ORIGIN_VERSION", "0.0.0-test"),
+    name: envOr("ORIGIN_NAME", "icy2-testclient-local"),
+    site: process.env.ORIGIN_SITE,
+    environment: process.env.ORIGIN_ENVIRONMENT,
+    logger: { warn: (msg, err) => console.warn(`[warn] ${msg}:`, err) },
+  };
+
+  let mockServer;
+  if (!config.serviceKey) {
+    console.log("ORIGIN_SERVICE_KEY not set — using a local mock check-in server");
+    const { server, url } = await startMockServer();
+    mockServer = server;
+    config.url = url;
+    config.serviceKey = "test-key";
+    config.installId = "test-install-id";
+  }
+
+  if (process.env.ORIGIN_INTERVAL_HOURS) {
+    config.intervalHours = Number(process.env.ORIGIN_INTERVAL_HOURS);
+  }
+
+  const client = new OriginClient(config);
+
+  try {
+    if (watch) {
+      console.log("watching — Ctrl-C to stop");
+      client.start();
+      await new Promise((resolve) => {
+        process.on("SIGINT", resolve);
+        process.on("SIGTERM", resolve);
+      });
+      client.stop();
+      return;
+    }
+
+    const resp = await client.checkinOnce();
+    console.log(JSON.stringify(resp, null, 2));
+  } finally {
+    mockServer?.close();
+  }
+}
+
+main().catch((err) => {
+  console.error("checkin failed:", err);
+  process.exitCode = 1;
+});