Switch to tsup for dual CJS/ESM packaging (0.0.8)

Fixes broken ESM resolution in Cloudflare Workers (workerd) by shipping
proper ESM (.mjs) alongside CJS (.js) with correct package.json exports
field. Replaces plain tsc build with tsup.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: AI Feature Agent

.gitignore

@@ -3,6 +3,7 @@ node_modules/
 
 # Build output
 lib/
+dist/
 
 # Logs
 *.log

package.json

@@ -1,18 +1,31 @@
 {
   "name": "xstate-migrate",
-  "version": "0.0.7",
+  "version": "0.0.8",
   "description": "A migration library for persisted XState machines",
-  "main": "lib/index.js",
-  "types": "lib/index.d.ts",
+  "main": "dist/index.js",
+  "module": "dist/index.mjs",
+  "types": "dist/index.d.ts",
+  "exports": {
+    ".": {
+      "import": {
+        "types": "./dist/index.d.mts",
+        "default": "./dist/index.mjs"
+      },
+      "require": {
+        "types": "./dist/index.d.ts",
+        "default": "./dist/index.js"
+      }
+    }
+  },
   "scripts": {
-    "build": "tsc",
+    "build": "tsup",
     "test": "jest",
     "test:coverage": "jest --coverage",
     "test:mutate": "stryker run",
     "lint": "eslint 'src/**/*.ts'",
     "format": "prettier --write 'src/**/*.ts'",
-    "prepare": "npm run build",
-    "prepublishOnly": "npm test && npm run lint"
+    "prepare": "pnpm run build",
+    "prepublishOnly": "pnpm test && pnpm run lint"
   },
   "keywords": [
     "xstate",
@@ -41,10 +54,11 @@
     "jest": "^29.7.0",
     "prettier": "^3.5.0",
     "ts-jest": "^29.4.6",
+    "tsup": "^8.5.1",
     "typescript": "^5.9.3",
     "xstate": "^5.28.0"
   },
   "files": [
-    "lib/**/*"
+    "dist/**/*"
   ]
 }