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>

package.json

@@ -2,18 +2,27 @@
   "name": "alex2node",
   "version": "1.5.2",
   "description": "A Node.js library for creating Alexa-compatible devices using MQTT, based on Alex2MQTT.",
-  "main": "dist/index.js",
-  "types": "dist/index.d.ts",
+  "type": "commonjs",
+  "main": "./dist/cjs/index.js",
+  "module": "./dist/esm/index.js",
+  "types": "./dist/types/index.d.ts",
   "exports": {
     ".": {
-      "require": "./dist/index.js"
-    }
+      "types": "./dist/types/index.d.ts",
+      "import": "./dist/esm/index.js",
+      "require": "./dist/cjs/index.js"
+    },
+    "./package.json": "./package.json"
+  },
+  "sideEffects": false,
+  "engines": {
+    "node": ">=18"
   },
-  "type": "commonjs",
   "scripts": {
-    "build": "tsc",
+    "build": "node scripts/build.mjs",
+    "check": "tsc --noEmit && tsc -p test/fixtures/tsconfig.json",
     "prepare": "npm run build",
-    "test": "node --test test/*.test.js"
+    "test": "node --test test/*.test.js test/*.test.mjs"
   },
   "keywords": [
     "alexa",
@@ -40,8 +49,7 @@
     "typescript": "^5.8.3"
   },
   "dependencies": {
-    "mqtt": "^5.10.3",
-    "uuid": "^11.0.3"
+    "mqtt": "^5.10.3"
   },
   "files": [
     "dist",