feat(utxo-staking): add ESM build support

Configure dual CommonJS/ESM output for utxo-staking module. Update package.json
with proper export conditions and file paths. Add ESM-specific tsconfig.

Issue: BTC-2732

Co-authored-by: llm-git <[email protected]>

Author: OttoAllmendinger

modules/utxo-staking/package.json

@@ -2,13 +2,30 @@
   "name": "@bitgo/utxo-staking",
   "version": "1.25.0",
   "description": "BitGo SDK for build UTXO staking transactions",
-  "main": "./dist/src/index.js",
-  "types": "./dist/src/index.d.ts",
+  "main": "./dist/cjs/src/index.js",
+  "module": "./dist/esm/index.js",
+  "browser": "./dist/esm/index.js",
+  "types": "./dist/cjs/src/index.d.ts",
   "files": [
-    "dist/src"
+    "dist/cjs",
+    "dist/esm"
   ],
+  "exports": {
+    ".": {
+      "import": {
+        "types": "./dist/esm/index.d.ts",
+        "default": "./dist/esm/index.js"
+      },
+      "require": {
+        "types": "./dist/cjs/src/index.d.ts",
+        "default": "./dist/cjs/src/index.js"
+      }
+    }
+  },
   "scripts": {
-    "build": "yarn tsc --build --incremental --verbose .",
+    "build": "npm run build:cjs && npm run build:esm",
+    "build:cjs": "yarn tsc --build --incremental --verbose .",
+    "build:esm": "yarn tsc --project tsconfig.esm.json",
     "fmt": "prettier --write .",
     "check-fmt": "prettier --check '**/*.{ts,js,json}'",
     "clean": "rm -r ./dist",
@@ -41,7 +58,6 @@
       ".ts"
     ]
   },
-  "type": "commonjs",
   "dependencies": {
     "@babylonlabs-io/babylon-proto-ts": "1.7.2",
     "@bitgo/babylonlabs-io-btc-staking-ts": "^3.1.0",

modules/utxo-staking/tsconfig.esm.json

@@ -0,0 +1,17 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "outDir": "./dist/esm",
+    "rootDir": "./src",
+    "module": "ES2020",
+    "target": "ES2020",
+    "moduleResolution": "bundler",
+    "lib": ["ES2020", "DOM"],
+    "declaration": true,
+    "declarationMap": true,
+    "skipLibCheck": true
+  },
+  "include": ["src/**/*", "src/babylon/*.json"],
+  "exclude": ["node_modules", "test", "dist", "scripts"],
+  "references": []
+}

modules/utxo-staking/tsconfig.json

@@ -1,7 +1,7 @@
 {
   "extends": "../../tsconfig.json",
   "compilerOptions": {
-    "outDir": "./dist",
+    "outDir": "./dist/cjs",
     "rootDir": ".",
     "typeRoots": ["./node_modules/@types", "../../node_modules/@types"],
     "allowJs": false,