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/fixtures/tsconfig.json

@@ -0,0 +1,11 @@
+{
+  "compilerOptions": {
+    "target": "ES2020",
+    "module": "Node16",
+    "moduleResolution": "Node16",
+    "strict": true,
+    "skipLibCheck": false,
+    "noEmit": true
+  },
+  "files": ["types.ts", "types.mts"]
+}

test/fixtures/types.mts

@@ -0,0 +1,10 @@
+// Compiled, never run: the same declarations as seen from an ES module. Without a "types" condition in "exports" the
+// import resolves to dist/esm/index.js, which has no declarations next to it, and this file fails with TS7016.
+import { Alex2MQTT, DEFAULT_HOST, EndpointHealth } from "alex2node";
+import type { Device } from "alex2node";
+
+const bridge = new Alex2MQTT("user", "password", "root", false, { host: DEFAULT_HOST });
+const devices: Device[] = bridge.getDevices();
+const health: EndpointHealth = EndpointHealth.OK;
+
+export { devices, health };

test/fixtures/types.ts

@@ -0,0 +1,36 @@
+// Compiled, never run (test/typings.test.js, npm run check): a CommonJS TypeScript consumer of the declarations in
+// dist/types, resolved through the package's "exports". A "@ts-expect-error" line fails the compile when the
+// declaration stops rejecting what follows it.
+import { ActionMapping, AlexaActions, AlexaInterfaceType, DisplayCategory, EndpointHealth, PowerController } from "alex2node";
+import type { Alex2MQTT, Alex2MQTTOptions, AlexaInterface, AlexaStatusMessage, ChangeCause, Device, SupportedMode } from "alex2node";
+
+declare const bridge: Alex2MQTT;
+declare const message: AlexaStatusMessage;
+declare const capability: AlexaInterface;
+
+const options: Alex2MQTTOptions = { host: "mqtt://127.0.0.1:1883", mqtt: { reconnectPeriod: 1000 }, log: (line) => line.length };
+const device: Device = bridge.registerDevice("Lamp", "lamp-1", [DisplayCategory.LIGHT, DisplayCategory.SWITCH]);
+const added: AlexaInterface = device.addCapability(AlexaInterfaceType.POWER_CONTROLLER, { proactivelyReported: true });
+
+// ActionMapping: the payload is optional
+const close = new ActionMapping([AlexaActions.Close], "TurnOn");
+capability.addActionMapping(close);
+
+// addHealthProp: the enum or its string values, chainable
+const chained: AlexaStatusMessage = message.addHealthProp(EndpointHealth.OK).addHealthProp("UNREACHABLE", 50);
+// @ts-expect-error not a connectivity value
+message.addHealthProp("ASLEEP");
+// @ts-expect-error a power state is ON or OFF
+message.addPowerControllerProp("ON ");
+message.addPowerControllerProp(PowerController.ON);
+
+// addSupportedModes: Mode objects, plain strings still accepted
+const mode: SupportedMode = { value: "Fan.Auto", modeResources: { friendlyNames: [{ "@type": "text", value: { text: "Auto", locale: "en-US" } }] } };
+capability.addSupportedModes([mode, "Fan.On"]);
+
+const cause: ChangeCause = "PHYSICAL_INTERACTION";
+const sent: Promise<string> = device.getChangeReport(cause).addPowerControllerProp(PowerController.OFF).send();
+// @ts-expect-error not a cause Alexa knows
+device.getChangeReport("BUTTON");
+
+export { options, added, chained, sent };