ci: move test actions to Node 24 runtimes

[tim8es]

Maintenance audit scope

Minimal CI-only maintenance from main @ e2abab5ad1c195c96233214847c7aedabb802d50.

Changes:

• actions/checkout@v4 -> actions/checkout@v5
• actions/setup-python@v5 -> actions/setup-python@v6

Reason: both old majors target Node 20 and emit deprecation warnings on current GitHub-hosted runners. The observed runner is 2.337.0, above the 2.327.1 minimum required by the Node 24 majors.

No production/runtime code changes. No branch-protection setting changes. Historical PR #36 is not merged or repurposed.

Audit findings outside this patch

• main branch protection / required checks are disabled (protected=false, no required status checks).
• repository rulesets are empty.
• PR ci: verify workflow v2 proposal RED/GREEN #36 remains open, draft, merged=false, with explicit Do not merge body.

Exact-head validation

Head: 7b74f99c862c77816ac0d7fe9c65948722d56c80
Run: 34425391198

• Python 3.10 job 102709417012: 327/327 OK
• Python 3.12 job 102709416808: 327/327 OK
• runner version: 2.337.0
• logs confirm actions/checkout@v5 and actions/setup-python@v6
• prior Node 20 deprecation warning is absent in both completed job logs

No merge performed.