refactor(scripts): rename index.mjs to main.mjs

Replace index.mjs barrel files with main.mjs for clarity:
- build/index.mjs → build/main.mjs
- fix/index.mjs → fix/main.mjs
- test/index.mjs → test/main.mjs

Author: jdalton

package.json

@@ -582,16 +582,16 @@
   },
   "sideEffects": false,
   "scripts": {
-    "build": "node scripts/build/index.mjs",
+    "build": "node scripts/build/main.mjs",
     "check": "node scripts/check.mjs",
     "clean": "node scripts/build/clean.mjs",
     "cover": "node scripts/test/cover.mjs",
-    "dev": "node scripts/build/index.mjs --watch",
+    "dev": "node scripts/build/main.mjs --watch",
     "fix": "node scripts/lint.mjs --fix",
     "lint": "node scripts/lint.mjs",
     "prepare": "husky",
     "prepublishOnly": "pnpm run build",
-    "test": "node scripts/test/index.mjs",
+    "test": "node scripts/test/main.mjs",
     "update": "node scripts/update.mjs"
   },
   "devDependencies": {