fix: address code review comments from PR #79

- Add TEST_GROUPS constant to eliminate magic number
- Use stdout for info messages, stderr for errors only
- Remove redundant comments and dead code
- Add CI check before copying coverage.info
- Unify variable declaration order
- Add port allocation explanation comment
- Restore /* 50ms */ inline comment
- Update CONTRIBUTING.md with build 1 description

CONTRIBUTING.md

@@ -91,7 +91,7 @@ set -e
 
 This will run the same tests that the CI runs and refuse the push if it fails.
 The CI script runs 4 parallel builds with different configurations, each with Valgrind and functional tests.
-Use `./ci-build.sh --coverage-only` to run only build 1 with coverage collection.
+Use `./ci-build.sh --coverage-only` to run only build 1 (full configuration with all optional components enabled) with coverage collection.
 
 Output shows test results per build:
 ```