Upgrade GitHub Actions to resolve Node.js 20 deprecation warnings

[civilizeddev]

CI runs are producing the following warning:

Node.js 20 actions are deprecated. The following actions are running on Node.js 20 and may not work as expected: actions/checkout@v4, coursier/cache-action@v6, olafurpg/setup-scala@v10. Actions will be forced to run with Node.js 24 by default starting June 2nd, 2026.

Reference: https://github.com/devsisters/shardcake/actions/runs/23176887451

Current action versions

ci.yml

Action	Current Version	Notes
actions/checkout	v4	Used in 3 jobs
olafurpg/setup-scala	v10	Used in 3 jobs
coursier/cache-action	v6	Used in 3 jobs

vuepress-deploy.yml

Action	Current Version	Notes
actions/checkout	master	Branch ref instead of tag
IT4Change/vuepress-build-and-deploy	master	Branch ref instead of tag

TODO

• Upgrade actions/checkout v4 → latest
• Upgrade coursier/cache-action v6 → latest
• Upgrade olafurpg/setup-scala v10 → latest (or evaluate replacement)
• Review and update actions in vuepress-deploy.yml
• Verify CI passes after upgrades

Deadline

Node.js 24 will be enforced starting June 2, 2026.