[smtmfft]

Summary

• restore GitHub Actions CI for pull requests and main
• run formatting, go vet, uncached full tests, and targeted race detection
• keep the workflow read-only and free of deployment, secrets, or SGX bootstrap actions

Verification

• gofmt -l $(git ls-files -- '*.go')
• go vet ./...
• go test -count=1 ./...
• go test -race -count=1 ./cmd/gaiko2 ./internal/api ./internal/tee
• Ruby YAML parse
• git diff --check