ci: improve test failure detection in parallel tests

1. ci-build.sh: Add verify_test_failure_detection() function
   - Tests that single test failures are properly detected
   - Tests that parallel test failures are properly detected
   - Runs at CI start to catch framework issues early

2. Makefile.am: Fix check-functional-parallel exit code handling
   - OLD: used 'wait' without checking individual exit codes
   - NEW: capture each PID and check exit code with 'wait $pid'
   - On failure: print the log file and set failed flag
   - Exit with error if any group failed

This ensures CI correctly fails when:
- Any unit test fails
- Any of the 4 functional test groups fails
- Any parallel build configuration fails

Makefile.am

@@ -311,17 +311,19 @@ tests_functionaltests_functionaltests_LDADD = -lcmocka -lstabber @FORKPTY_LIB@
 check-functional-parallel: tests/functionaltests/functionaltests
 	@echo "Running functional tests in parallel (4 groups)..."
 	@mkdir -p $(builddir)/test-logs
-	@( \
-		./tests/functionaltests/functionaltests 1 > $(builddir)/test-logs/group1.log 2>&1 & \
-		./tests/functionaltests/functionaltests 2 > $(builddir)/test-logs/group2.log 2>&1 & \
-		./tests/functionaltests/functionaltests 3 > $(builddir)/test-logs/group3.log 2>&1 & \
-		./tests/functionaltests/functionaltests 4 > $(builddir)/test-logs/group4.log 2>&1 & \
-		wait \
-	) && ( \
-		echo "=== Test Results ==="; \
-		grep -E 'PASSED|FAILED|Running' $(builddir)/test-logs/group*.log; \
-		! grep -q FAILED $(builddir)/test-logs/group*.log \
-	)
+	@failed=0; \
+	./tests/functionaltests/functionaltests 1 > $(builddir)/test-logs/group1.log 2>&1 & pid1=$$!; \
+	./tests/functionaltests/functionaltests 2 > $(builddir)/test-logs/group2.log 2>&1 & pid2=$$!; \
+	./tests/functionaltests/functionaltests 3 > $(builddir)/test-logs/group3.log 2>&1 & pid3=$$!; \
+	./tests/functionaltests/functionaltests 4 > $(builddir)/test-logs/group4.log 2>&1 & pid4=$$!; \
+	wait $$pid1 || { echo "Group 1 FAILED (exit $$?)"; cat $(builddir)/test-logs/group1.log; failed=1; }; \
+	wait $$pid2 || { echo "Group 2 FAILED (exit $$?)"; cat $(builddir)/test-logs/group2.log; failed=1; }; \
+	wait $$pid3 || { echo "Group 3 FAILED (exit $$?)"; cat $(builddir)/test-logs/group3.log; failed=1; }; \
+	wait $$pid4 || { echo "Group 4 FAILED (exit $$?)"; cat $(builddir)/test-logs/group4.log; failed=1; }; \
+	echo "=== Test Results Summary ==="; \
+	grep -E 'PASSED|FAILED|Running' $(builddir)/test-logs/group*.log || true; \
+	if [ $$failed -ne 0 ]; then echo "FUNCTIONAL TESTS FAILED"; exit 1; fi; \
+	echo "All functional test groups passed!"
 endif
 endif