fix(clang-tidy): re-enable bugprone-unused-return-value

[vish0012]

Description

Re-enables bugprone-unused-return-value in .clang-tidy-ci.

The check was suppressed in #12431. This PR addresses the 2 reported errors in system/autoware_system_monitor listed in #12450.

Refs #12450

Approach

Both errors came from Boost.Asio calls where the returned boost::system::error_code was ignored, even though the code already had an error_code variable and checked it immediately afterward.

This PR assigns the returned value back to error_code, preserving the existing logic while satisfying bugprone-unused-return-value.

Changed calls:

error_code = acceptor_->accept(*socket_, error_code);
error_code = socket_->connect(endpoint, error_code);

Affected files:

• system/autoware_system_monitor/reader/traffic_reader/traffic_reader_service.cpp
• system/autoware_system_monitor/src/net_monitor/net_monitor.cpp

How to reproduce

From the colcon workspace root:

cd ~/autoware_clang_tidy
source /opt/ros/humble/setup.bash

mkdir -p /tmp/clang-tidy-result

colcon build --packages-up-to autoware_system_monitor \
  --cmake-args -DCMAKE_EXPORT_COMPILE_COMMANDS=1

run-clang-tidy -p build/ \
  -config="$(cat src/autoware_universe/.clang-tidy-ci)" \
  -export-fixes /tmp/clang-tidy-result/fixes.yaml \
  -j $(nproc) autoware_system_monitor \
  > /tmp/clang-tidy-result/report.log 2>&1

To check the reported errors:

grep -n "bugprone-unused-return-value" /tmp/clang-tidy-result/report.log | grep "error:" || echo "0 unused-return-value errors"

Verification

Before the fix, the following 2 errors were reproduced:

system/autoware_system_monitor/reader/traffic_reader/traffic_reader_service.cpp:83
system/autoware_system_monitor/src/net_monitor/net_monitor.cpp:667

After the fix, autoware_system_monitor builds successfully and run-clang-tidy reports:

0 unused-return-value errors

Notes

The only .clang-tidy-ci change is removing the suppression line for this check:

-  -bugprone-unused-return-value"

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