Migrate Cloudflare Pages uploads off Node 20/refined action

[maxffarrell]

The current Cloudflare Pages upload workflows should move off AdrianGonz97/refined-cf-pages-action@v1.

Why:

• GitHub is deprecating Node 20 for JavaScript actions. Runners begin using Node 24 by default on June 16, 2026, and GitHub says Node 20 will be removed from runners later in fall 2026: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/
• AdrianGonz97/refined-cf-pages-action currently declares runs.using: node20 in action.yml: https://github.com/AdrianGonz97/refined-cf-pages-action/blob/main/action.yml
• The refined action is an opinionated fork of Cloudflare's Pages action. Cloudflare has archived cloudflare/pages-action, marks it deprecated, and recommends cloudflare/wrangler-action for Pages deployments: https://github.com/cloudflare/pages-action

In this repo, the affected workflows are:

• .github/workflows/deploy-preview.yml
• .github/workflows/deploy-svelte-4.yml
• .github/workflows/deploy-tailwind-3.yml

The migration should keep the existing direct-upload behavior, but use cloudflare/wrangler-action@v3 with wrangler pages deploy so the deploy path is no longer blocked by a Node 20 action runtime or by the deprecated Pages action lineage.

Related PR: #2736