Two sendspin clients are unable to play simultaneously in dual mono setup

Reproduce the dual-mono setup with Sendspin 5.9.0 and MA 2.8.1, starting playback on both clients. Trace aiosendspin.client.client.py at _handle_audio_chunk and sendspin.audio_connector.py at AudioStreamHandler._on_audio_chunk, then verify both clients can play simultaneously without the audio-worker or output-device errors.

With Sendspin 5.9.0 and MA 2.8.1 both Sendspin clients are able to start as long as no music is playing. When starting playback and linking clients, slave throws:

ERROR:aiosendspin.client.client:Error in audio chunk callback <bound method AudioStreamHandler._on_audio_chunk of <sendspin.audio_connector.AudioStreamHandler object at 0x7f8d2bb770>>
Traceback (most recent call last):
File "/var/lib/sendspin-olohuone/.local/share/uv/tools/sendspin/lib/python3.13/site-packages/aiosendspin/client/client.py", line 876, in _handle_audio_chunk
callback(timestamp_us, payload, self._current_audio_format)
~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/var/lib/sendspin-olohuone/.local/share/uv/tools/sendspin/lib/python3.13/site-packages/sendspin/audio_connector.py", line 451, in _on_audio_chunk
raise RuntimeError("Audio worker is not running")
RuntimeError: Audio worker is not running

Then for as long as the other sendspin instance is running, the crashed instance is unable to start and throws:

Error: No output device matching 'olohuone'

When restarting both instances, both are again able to start.

So either one can be used to play music, but not simultaneously.

Originally posted by @rvk in #58