Fix signal handler flood: only install in main process

setup_signal_handlers() was being called in every ruffus worker
subprocess (each one inherits the parent's handler via fork). When
the pipeline exits and SIGTERM is broadcast to the process group,
every worker logs 'Received signal 15. Starting clean-up.' and runs
cleanup in parallel, producing dozens of duplicate log lines.

Fix: skip handler installation in non-main processes using
multiprocessing.current_process().name.

Author: Acribbs

cgatcore/pipeline/execution.py

@@ -923,7 +923,15 @@ def cleanup_all_jobs(self):
         self.active_jobs.clear()  # Clear the list after cleanup
 
     def setup_signal_handlers(self):
-        """Set up signal handlers to clean up jobs on SIGINT and SIGTERM."""
+        """Set up signal handlers to clean up jobs on SIGINT and SIGTERM.
+
+        Only installed in the main process; ruffus worker subprocesses inherit
+        signal dispositions from the parent but should not run cleanup themselves,
+        otherwise every worker logs the signal and tries to clean up in parallel.
+        """
+        import multiprocessing
+        if multiprocessing.current_process().name != 'MainProcess':
+            return
 
         def signal_handler(signum, frame):
             self.logger.info(f"Received signal {signum}. Starting clean-up.")