CI: Race detector, coverage tracking, build.yml consolidation

[erdemtuna]

Source: codeFindings.md Section 5

Three CI/CD gaps:

1. Race detector: go test -race requires CGO. CI may need CGO_ENABLED=1 to enable race detection.

2. Coverage tracking: Coverage artifact is uploaded but not tracked over time. Add codecov or coveralls integration to detect coverage regressions.

3. build.yml redundant: Both build.yml and release.yml build binaries on tag push. Could consolidate to avoid duplicate work.