fix: bump github actions to node24 runtimes

[talalashraf]

GitHub is removing Node ≤20 action runtimes from Actions runners on 2026-09-16, with a forced Node 24 default starting 2026-06-16 (changelog). Actions updated to their Node 24 releases:

• actions/checkout v3 → v6
• actions/setup-node v3 → v6
• codecov/codecov-action v3 → v7

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (9f457b6) to head (db69fb9).

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #113   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines          210       210           
  Branches        42        42           
=========================================
  Hits           210       210           

Flag	Coverage Δ
unittests	100.00% <ø> (ø)

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[tobernguyen]

Reviewed for the PLA-1666 Node 24 GitHub Actions runtime rollout: confirmed this is a clean, mechanical GitHub Actions version bump (no application/logic/secret/permission changes). Approving.