Fix thread safety in RabbitMQ manager

[marcomelloni]

Summary

• publish messages through the connection thread via add_callback_threadsafe
• adjust RabbitMQ manager tests to expect thread‑safe scheduling

Testing

• pytest -q (fails: ModuleNotFoundError: No module named 'blinker')

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https://chatgpt.com/codex/tasks/task_e_688230105bec8333b37b4a2b1433c35e

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 86.20690% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...matlab_agent/src/comm/rabbitmq/rabbitmq_manager.py	73.33%	4 Missing ⚠️

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