build: dual CJS/ESM output, ES2020 target, Node 18 floor

"exports" gains "import" and "types" next to "require": import "alex2node" failed with
ERR_PACKAGE_PATH_NOT_EXPORTED. scripts/build.mjs compiles src/ to dist/cjs, dist/esm and dist/types in a staging
directory and swaps them in only when both compiler runs passed. "main" and "types" follow for resolvers that do
not read "exports". Target ES6 -> ES2020, "engines": node >= 18, relative imports carry ".js" for Node's ESM loader.
uuid gives way to crypto.randomUUID(); mqtt is the only runtime dependency left.

Tests load the package by name. New: both entry points, the modules the builds import, dist/ equal to a fresh
build, a round trip on the ES module build, and two compiled type fixtures in place of the .d.ts regexes.
22 tests pass in 5.7 s. dist/: 16 files, 79,711 B -> 25 files, 132,291 B; the npm tarball is 25,125 B.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

test/packaging.test.mjs

@@ -0,0 +1,39 @@
+// The ES module build, imported the way an ES module consumer writes it, on the broker: a build that loads but
+// cannot reach mqtt or one of its own files fails here.
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { Alex2MQTT, AlexaInterfaceType, DisplayCategory, EndpointHealth, PowerController } from "alex2node";
+import harness from "./helpers/harness.js";
+
+const { setup, directive, until } = harness;
+
+test("import { Alex2MQTT } from \"alex2node\": discovery, a directive and a change report on the ES module build", async () => {
+  const { alexa, bridge } = await setup(Alex2MQTT, "root");
+  const lamp = bridge.registerDevice("Lamp", "lamp-1", DisplayCategory.LIGHT);
+  lamp.addCapability(AlexaInterfaceType.POWER_CONTROLLER, { proactivelyReported: true });
+  lamp.addCapability(AlexaInterfaceType.ENDPOINT_HEALTH);
+  lamp.on("Event", (request) => {
+    lamp.getStatusMessage(request.header.correlationToken, true)
+      .addHealthProp(EndpointHealth.OK)
+      .addPowerControllerProp(PowerController.ON)
+      .send();
+  });
+
+  alexa.publish("root/discover", { namespace: "Alexa.Discovery", name: "Discover" });
+  await until(() => alexa.on("root/discover_r").length === 1, 3000, "discovery reply");
+  const [endpoints] = alexa.on("root/discover_r");
+  assert.deepEqual(endpoints.map((e) => e.endpointId), ["lamp-1"]);
+  assert.deepEqual(endpoints[0].capabilities.map((c) => c.interface), ["Alexa.PowerController", "Alexa.EndpointHealth"]);
+
+  alexa.send("root", directive("Alexa.PowerController", "TurnOn", "lamp-1", "ct1"));
+  await until(() => alexa.on("root/lamp-1/alexaResponce").length === 1, 3000, "directive response");
+  const [response] = alexa.on("root/lamp-1/alexaResponce");
+  assert.equal(response.event.header.name, "Response");
+  assert.equal(response.event.header.correlationToken, "ct1");
+  // crypto.randomUUID() writes the messageId: a version 4 UUID, as uuid's v4() did
+  assert.match(response.event.header.messageId, /^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/);
+
+  assert.equal(await lamp.getChangeReport().addPowerControllerProp(PowerController.OFF).send(), "root/changeReport");
+  await until(() => alexa.on("root/changeReport").length === 1, 3000, "change report");
+  assert.equal(alexa.on("root/changeReport")[0].event.payload.change.properties[0].value, "OFF");
+});