fix(examples): make async_call.py main synchronous to avoid loop conflict

Updated examples/async_call.py to use a synchronous main entry point. This prevents a RuntimeError caused by prompt-toolkit attempting to start its own asyncio loop while one was already running in the same thread. The example's core functionality of bridging sync and async code remains intact through its use of a background thread for asynchronous tasks.

Author: tleonhardt

examples/async_call.py

@@ -65,9 +65,9 @@ def do_hello_world(self, _: str) -> None:
         self.poutput('Hello World')
 
 
-async def main() -> int:
+def main() -> int:
     """
-    Having this async ensures presence of the top level event loop.
+    Main entry point for the example.
     """
     app = AsyncCallExample()
     app.set_window_title("Call to an Async Function Test")
@@ -77,4 +77,4 @@ async def main() -> int:
 if __name__ == '__main__':
     import sys
 
-    sys.exit(asyncio.run(main(), debug=True))
+    sys.exit(main())