chore: update GitHub Actions to Node.js 24-compatible versions

[rappdw]

Summary

• Update all GitHub Actions workflow action versions to support Node.js 24, ahead of the June 2, 2026 deadline when GitHub will force Node.js 24 as the default runtime
• Actions updated across ci.yml, integration.yml, and release.yml:
  • actions/checkout: v4 -> v5
  • actions/setup-python: v4 -> v5
  • actions/cache: v3 -> v5
  • actions/upload-artifact: v4 -> v5
  • actions/download-artifact: v4 -> v5
  • softprops/action-gh-release: v1 -> v2 (also removed now-unnecessary GITHUB_TOKEN env block)
  • pypa/cibuildwheel: v2.16.5 -> v2.23.4
• Actions kept at current versions (no Node.js runtime dependency or already compatible): irongut/CodeCoverageSummary@v1.3.0 (Docker), schneegans/dynamic-badges-action@v1.7.0, marocchino/sticky-pull-request-comment@v2, ilammy/msvc-dev-cmd@v1, pypa/gh-action-pypi-publish@release/v1 (Docker)

Test plan

• Verify CI workflow runs successfully on this PR
• Confirm no Node.js 20 deprecation warnings appear in workflow logs

🤖 Generated with Claude Code

[github-actions]

Package	Line Rate	Complexity	Health
.	68%	0	➖
core	92%	0	✔
reference	98%	0	✔
sparse	94%	0	✔
sparse.csgraph	58%	0	❌
types	100%	0	✔
util	67%	0	➖
Summary	73% (1489 / 2036)	0	➖

Minimum allowed line rate is 65%