serial-console: decode binary WebSocket frames before printing

websocket-client delivers binary frames as Python bytes objects.
Passing bytes directly to PC.print() causes print() to render them
as raw repr strings (e.g. b'\r\r\n', b'login: ') instead of decoded
text, which corrupts the serial console output in WSL and other
non-Windows environments.

Fix this by decoding bytes to str with UTF-8 (replacing invalid
sequences) in on_message() before calling PC.print().

Fixes: Azure/azure-cli#33164

Signed-off-by: Praveen K Paladugu <prapal@linux.microsoft.com>
Signed-off-by: GitHub Copilot <copilot@github.com>

Author: praveen-pk

src/serial-console/azext_serialconsole/custom.py

@@ -438,6 +438,8 @@ def on_message(_, message):
                 GV.loading = False
                 PC.clear_screen()
             else:
+                if isinstance(message, bytes):
+                    message = message.decode('utf-8', errors='replace')
                 PC.print(message)
 
         def on_error(*_):