Migrate GitHub Actions workflows off deprecated Node.js 20 actions

[a-a-k]

Problem

GitHub Actions runs for \ci\ and \
elease\ currently emit the Node.js 20 deprecation warning for \�ctions/checkout@v4\, \�ctions/setup-python@v5\, and \�zure/setup-helm@v4\.

GitHub indicates Node.js 24 becomes the default for JavaScript actions on 2026-06-02. This is not blocking current releases, but it is now an explicit maintenance item.

Scope

• review newer action versions or replacement actions that support Node.js 24
• update both .github/workflows/ci.yml and .github/workflows/release.yml
• keep current verification coverage intact, including pinned GHCR smoke in CI and release publishing
• remove the deprecation warning from successful workflow runs

Acceptance

• \ci\ succeeds without the Node.js 20 deprecation annotation
• \
  elease\ succeeds without the Node.js 20 deprecation annotation
• no regression in chart packaging, asset packaging, pinned-image smoke, or GitHub release publishing

[a-a-k]

Update after merging and releasing \�0.3.0:\n\n- \�ctions/checkout\ was moved to \�6\n- \�ctions/setup-python\ was moved to \�6\n- \�zure/setup-helm\ was moved to \�4.3.1\n\nObserved result on \ci\ run 23407592947 for commit \ce14aef6dd2ee99571a7ef4d6a211f9cf9173aba: the workflow succeeds, but GitHub still emits the Node.js 20 deprecation annotation for \�zure/setup-helm@v4.3.1.\n\nThat means issue #20 is not yet fully resolved and should remain open. The remaining work is to replace or remove \�zure/setup-helm\ in .github/workflows/ci.yml\ and .github/workflows/release.yml\ with a Node 24-safe Helm installation path, then re-run \ci\ and
elease\ without the annotation.

[a-a-k]

Release update (2026-05-01): mb3r-stack v0.3.1 release workflow still reports a Node.js 20 deprecation annotation for azure/setup-helm@v4.3.1.

Run: https://github.com/MB3R-Lab/mb3r-stack/actions/runs/25205623771

This confirms the item remains a real follow-up after the v0.3.1 package release. Upstream Bering/Sheaft release workflows also emitted Node.js 20 annotations for their action dependencies, so the broader maintenance pass should cover all three repos rather than only the stack chart packaging path.