pnpm 9 requires Node.js ≥ 18.12.0 (dropped Node 16 support in pnpm 9.0.0, April 2024). Node.js 14 (EOL April 2023) does not satisfy this. Running `pnpm install` on Node 14 with pnpm 9 produces an immediate engines check failure. Upgrade to Node.js 20 LTS.