Fix: tests workflow

[bxvtr]

Summary

Fix CI workflow by installing the build package.

Motivation

The GitHub Actions runner does not include the build module by default, causing wheel builds to fail in the test pipeline.

Type of Change

• Bug fix
• New feature
• Performance improvement
• Refactor
• Documentation
• Breaking change

Technical Details

Adds an explicit pip install build step prior to the wheel build stage in the test workflow.

Determinism & Reproducibility

• Change preserves deterministic behavior
• Tests confirm reproducibility
• No hidden state introduced

Performance Impact

• No measurable impact
• Benchmarks included
• Performance improvement

Tests

• Unit tests added/updated
• Integration tests added/updated
• Existing tests pass

Breaking Changes

None.

Checklist

• Code follows project style guidelines
• Self-review completed
• Documentation updated (if needed)