The collector subprocess was spawned via 'python3 -m decnet.cli collect'
but cli.py had no 'if __name__ == __main__: app()' guard. Python executed
the module, defined all functions, then exited cleanly with code 0 without
ever calling the collect command. No output, no log file, exit 0 — silent
non-start every time.
Also route collector stderr to <log_file>.collector.log so future crashes
are visible instead of disappearing into DEVNULL.