chore(toolchain): pin pnpm 12.5.1 and require Node 24

package.json

@@ -3,6 +3,11 @@
     "private": true,
     "version": "1.0.0",
     "type": "module",
+    "packageManager": "pnpm@12.5.1",
+    "engines": {
+        "node": ">=24.0.0",
+        "pnpm": ">=12.0.0"
+    },
     "scripts": {
         "dev": "tsx script/dev.ts",
         "test": "vitest",