- Add Magic Nix Cache for 3-9x faster builds
- Add --use-github-releases to only update stable versions
- Remove SKIP_PACKAGES, use dynamic discovery via passthru.updateScript
- Implement 4 concurrent update jobs for 4x speedup
- Add nix flake check for comprehensive validation
- Collect all build failures instead of failing on first
- Fix git reset bug that was destroying commits
- Add job timeout to prevent hanging
- Add detailed job summary and log artifacts
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