fix(examples): wrap all of them into a main function (#2524)

examples/tutorial/async-inf/policy_server.py

@@ -1,11 +1,17 @@
 from lerobot.async_inference.configs import PolicyServerConfig
 from lerobot.async_inference.policy_server import serve
 
-host = ...  # something like "127.0.0.1" if you're exposing to localhost
-port = ...  # something like 8080
 
-config = PolicyServerConfig(
-    host=host,
-    port=port,
-)
-serve(config)
+def main():
+    host = ...  # something like "127.0.0.1" if you're exposing to localhost
+    port = ...  # something like 8080
+
+    config = PolicyServerConfig(
+        host=host,
+        port=port,
+    )
+    serve(config)
+
+
+if __name__ == "__main__":
+    main()