Fix system_message forwarding

[Wovchena]

This PR ensures the system_message parameter is correctly forwarded through the continuous‐batching pipeline and validates this in Python tests.

• Fixes the C++ adapter and pipeline to pass system_message to the underlying implementation
• Cleans up stray semicolons in C++ method definitions
• Updates Python tests to include a system_message case

[Copilot]

Pull Request Overview

This PR ensures the system_message parameter is correctly forwarded through the continuous‐batching pipeline and validates this in Python tests.

• Fixes the C++ adapter and pipeline to pass system_message to the underlying implementation
• Cleans up stray semicolons in C++ method definitions
• Updates Python tests to include a system_message case

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
tests/python_tests/test_llm_pipeline.py	Added a system_message case and a greeting question to the test list
src/cpp/src/llm/pipeline_continuous_batching_adapter.hpp	Forward system_message in start_chat override
src/cpp/src/continuous_batching/pipeline.cpp	Removed redundant semicolons after function definitions

Comments suppressed due to low confidence (2)

tests/python_tests/test_llm_pipeline.py:146

• The test now includes a custom system_message but doesn't assert that the output reflects the 'Hola!' prefix. Add an assertion to verify that generated responses start with 'Hola!'.

(dict(max_new_tokens=20), "You are a helpful assistant. Start every message with 'Hola!'")

src/cpp/src/llm/pipeline_continuous_batching_adapter.hpp:207

• [nitpick] The API signature for start_chat has changed to accept a system_message. Consider updating or adding a doc comment above this method to explain the new parameter and its expected behavior.

void start_chat(const std::string& system_message) override {