Track the v2 test-framework modernization introduced by PR #59.\n\nScope:\n- Add GoogleTest and make GoogleMock available in the v2 Bazel module.\n- Migrate functional v2 tests from custom assert-based mains.\n- Preserve and document Google Benchmark usage.\n- Add v2 coding and testing guidance.\n- Resolve SonarCloud coverage and code-quality findings.
Track the v2 test-framework modernization introduced by PR #59.\n\nScope:\n- Add GoogleTest and make GoogleMock available in the v2 Bazel module.\n- Migrate functional v2 tests from custom assert-based mains.\n- Preserve and document Google Benchmark usage.\n- Add v2 coding and testing guidance.\n- Resolve SonarCloud coverage and code-quality findings.