ci: refactor ci-build.sh with constants and helper functions

- Add CMOCKA_PASSED_PATTERN, CMOCKA_FAILED_PATTERN constants
- Add COVERAGE_PATTERNS constant for lcov extraction
- Add parse_build_stats() function for parsing build logs
- Add extract_test_count() helper function
- Organize code into sections: Constants, Helper Functions, Test Verification

CONTRIBUTING.md

@@ -91,12 +91,15 @@ 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.
-Build 1 also collects code coverage (lines, functions, branches).
+Use `./ci-build.sh --coverage-only` to run only build 1 with coverage collection.
 
 Output shows test results per build:
 ```
-✓ Build 1 passed (unit: 437/0, func: 69/0, cov: L:27.5% F:36.2% B:18.1%, 5m39s)
-✓ Build 2 passed (unit: 398/0, func: 69/0, 5m00s)
+✓ BUILD 1 PASSED
+  Unit tests:       437 passed, 0 failed
+  Functional tests: 69 passed, 0 failed
+  Coverage:         Lines: 27.5% | Functions: 36.2% | Branches: 18.1%
+  Duration:         5m39s
 ```
 
 Note that it will run on the actual content of the repository directory and not