Fix deploy workflow failure by upgrading Node runtime for Hugo/PostCSS

[Copilot]

The deploy GitHub Actions job failed during Hugo asset processing because the workflow pinned Node 16, while the current Hugo/PostCSS execution path uses Node permission-model flags unsupported by Node 16.

• Root cause

  • hugo PostCSS transform invoked Node with permission flags (--permission, --allow-fs-read, etc.).
  • Node 16 rejects these flags, causing the build to panic and the deploy job to fail.

• Workflow update

  • Updated .github/workflows/gh-pages.yml to use a modern Node runtime in the deploy build step:
    • actions/setup-node@v3 node-version: '16' → node-version: '22'

• Minimal diff

  - with:
  -   node-version: '16'
  + with:
  +   node-version: '22'