Bump pinned GitHub Actions to latest release commit

[Copilot]

The build workflow was still pinned to an older actions/checkout commit. This updates the workflow to the latest release commit while keeping the action reference fully pinned.

• Workflow dependency update

  • Bump actions/checkout from v4.1.7 to v6.0.2
  • Replace the previous pinned SHA with the release commit for v6.0.2

• Pinning policy preserved

  • Keep the workflow on an immutable commit reference rather than a floating tag
  • Update the inline version annotation to match the new pinned release

- name: Checkout code
  uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2