Fix exit method to use sys.exit for proper cleanup

Change RNS.__init__.py exit method from os._exit to sys.exit to allow
proper cleanup and exception handling. Keep panic method using os._exit
for immediate termination in unrecoverable scenarios.

RNS/__init__.py

@@ -382,7 +382,7 @@ def exit(code=0):
     if not exit_called:
         exit_called = True
         Reticulum.exit_handler()
-        os._exit(code)
+        sys.exit(code)
 
 class Profiler:
     _ran = False