Update Pages workflow actions for Node 24 and SHA pinning

[intel352]

Problem

The main-branch Build & Deploy Registry run after merging #230 succeeded, but GitHub emitted a Node.js 20 deprecation annotation:

Node.js 20 actions are deprecated. The following actions are running on Node.js 20 and may not work as expected: actions/checkout@v4, actions/upload-artifact@v4. Actions will be forced to run with Node.js 24 by default starting June 16th, 2026. Node.js 20 will be removed from the runner on September 16th, 2026.

Run: https://github.com/GoCodeAlone/workflow-registry/actions/runs/27073168944

The workflow currently uses major-version refs such as actions/checkout@v4 and Pages actions that transitively use actions/upload-artifact@v4. Per the workflow hardening direction, provider and CI workflow refs should be pinned to immutable SHAs, with the human-readable version retained in a comment.

Expected work

• Update .github/workflows/build-and-deploy.yml to use current Node 24-compatible action versions.
• Pin third-party action refs by SHA and include version comments.
• Confirm any transitive Pages action warnings are gone, or document any GitHub-owned action that cannot yet avoid the warning.
• Run the registry workflow validation before merging.