ci: improve CI stability with parallel builds, Valgrind, and coverage

ci-build.sh

@@ -261,7 +261,15 @@ build_and_test() {
             if command -v lcov >/dev/null 2>&1; then
                 lcov --capture --directory . --output-file coverage.info \
                     --rc lcov_branch_coverage=1 --ignore-errors inconsistent 2>&1 || true
-                lcov --remove coverage.info '/usr/*' '*/tests/*' --output-file coverage.info \
+                # Remove test files, stubs, system headers - only keep src/ production code
+                lcov --remove coverage.info \
+                    '/usr/*' \
+                    '*/tests/*' \
+                    '*test*.c' \
+                    '*stub*.c' \
+                    '*/functionaltests/*' \
+                    '*/unittests/*' \
+                    --output-file coverage.info \
                     --rc lcov_branch_coverage=1 --ignore-errors inconsistent 2>&1 || true
                 if [ -f coverage.info ] && [ -s coverage.info ]; then
                     local summary