Update GitHub Actions to latest versions

[epompeii]

Summary

• actions/cache v4 → v5
• actions/download-artifact v4 → v7
• actions/upload-artifact v4 → v6
• mlugg/setup-zig v1 → v2
• lycheeverse/lychee-action v2.3.0 → v2.4.1

All upgrades are backward compatible — no workflow input/config changes needed. upload-artifact@v6 and download-artifact@v7 are fully compatible with each other.

Supersedes #607, #608, #630, #631, #632

Test plan

• CI workflows pass with the updated action versions
• Artifact upload/download works correctly across jobs

https://claude.ai/code/session_01GvcMR9yr5MKruNmrXWadDn

[github-actions]

🤖 Claude Code Review

PR: #738
Base: devel
Head: claude/update-github-actions-IMVof
Commit: 87ba26158d41cc11df7f03abd7e50658413c3334

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PR Review: Update GitHub Actions to latest versions

Summary

Two commits updating GitHub Actions dependencies across 8 CI workflow files. Pure version bumps, no logic changes.

Version Changes

Action	Old	New	Status
actions/cache	v4	v5	OK
actions/upload-artifact	v4	v7	OK
actions/download-artifact	v4	v8	OK
lycheeverse/lychee-action	v2.3.0	v2.4.1	OK
mlugg/setup-zig	v1	v2	OK

Issues

1. upload-artifact v7 / download-artifact v8 version mismatch
The upload-artifact is at v7 and download-artifact is at v8. This is intentional and correct — these actions moved to independent versioning. However, it's worth confirming that artifacts uploaded with v7 are compatible with downloads via v8. Per the GitHub docs, v7 upload is the counterpart to v8 download (both use the same underlying artifact backend), so this pairing is correct.

2. No pinning to full SHA
All actions use tag-based references (e.g., @v5) rather than SHA-pinned references (e.g., @abc123). This is the existing pattern in the repo so it's consistent, but SHA pinning is a security best practice to prevent tag-hijacking supply chain attacks. Consider pinning to full commit SHAs for third-party actions, especially mlugg/setup-zig and lycheeverse/lychee-action which are community-maintained.

3. actions/checkout not updated
The diff shows actions/checkout@v6 is already in use (appears in context lines). This is current, so no issue.

Verdict

Looks good. The changes are mechanical, consistent across all workflows, and use the correct version pairings. The only actionable suggestion is considering SHA pinning for supply chain security, but that's a pre-existing pattern rather than a regression introduced by this PR.

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_{Model: claude-opus-4-6}