refactor: use errors.As/Is for idiomatic error checks - #363

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@0ad4b8fadaa221de15dcec353f45205ec38ea70b. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/