enforce pnpm without packageManager field

Author: emmnull

package.json

@@ -9,6 +9,7 @@
     "check:watch": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json --watch",
     "dev": "vite dev",
     "format": "npm run lint:fix && npm run prettier:fix",
+    "preinstall": "npx only-allow pnpm",
     "lint": "eslint .",
     "lint:fix": "eslint --fix .",
     "prepare": "svelte-kit sync",
@@ -60,6 +61,7 @@
     "globals": "^16.3.0",
     "mdsvex": "^0.12.6",
     "music-metadata": "^11.7.3",
+    "only-allow": "^1.2.1",
     "prettier": "^3.6.2",
     "prettier-plugin-jsdoc": "^1.3.3",
     "prettier-plugin-packagejson": "^2.5.19",
@@ -79,6 +81,5 @@
     "vite": "^7.0.6",
     "vitest": "^3.2.4",
     "zod": "^4.0.15"
-  },
-  "packageManager": "pnpm@10.6.5+sha512.cdf928fca20832cd59ec53826492b7dc25dc524d4370b6b4adbf65803d32efaa6c1c88147c0ae4e8d579a6c9eec715757b50d4fa35eea179d868eada4ed043af"
+  }
 }