Introduce command-based simulation control

[marcomelloni]

Summary

• add CommandRegistry to manage stop/run commands
• support STOP/RUN/CHECK messages in Matlab agent message handler
• make streaming and interactive controllers respect stop commands
• document new control commands in agent README

Testing

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

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https://chatgpt.com/codex/tasks/task_e_6880b6eedd288333820f17feeed13d25

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 50.00000% with 17 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
.../matlab_agent/src/comm/rabbitmq/message_handler.py	16.66%	10 Missing ⚠️
agents/matlab/matlab_agent/src/core/interactive.py	20.00%	4 Missing ⚠️
agents/matlab/matlab_agent/src/core/streaming.py	60.00%	2 Missing ⚠️
agents/matlab/matlab_agent/src/utils/commands.py	91.66%	1 Missing ⚠️

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