Fix typos and Int64 handling, add test

[lreiher]

Summary

• fix typo in mqtt2float/mqtt2int error messages
• correct Int64 handling in fixedMqtt2PrimitiveRos
• fix misspelling in comment
• fix README links
• add regression test for Int64 conversion

Testing

• colcon test (fails: colcon not found)

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https://chatgpt.com/codex/tasks/task_e_684144b112d48321b5197a3d173bca14

[Copilot]

Pull Request Overview

This PR fixes typos in exception messages, corrects Int64 handling in primitive conversion, updates a comment, fixes a README link, and adds a regression test for Int64 conversion.

• Corrected spelling of “characters” in mqtt2float/mqtt2int error messages
• Changed Int32 → Int64 in fixedMqtt2PrimitiveRos and added a gtest for Int64
• Fixed a comment typo, updated CMakeLists to enable testing, and corrected the UInt64 link in README

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
mqtt_client/src/MqttClient.ros2.cpp	Spelling fixes in exception text; Int64 conversion
mqtt_client/include/MqttClient.ros2.hpp	Fixed typo in comment
mqtt_client/test/test_fixed_primitive.cpp	Added regression test for Int64 conversion
mqtt_client/CMakeLists.txt	Enabled testing blocks and gtest configuration
README.md	Corrected broken link for std_msgs/UInt64

Comments suppressed due to low confidence (2)

mqtt_client/test/test_fixed_primitive.cpp:22

• Consider adding a test case for a negative Int64 value (e.g., "-123") to ensure fixedMqtt2PrimitiveRos handles negative conversions correctly.

EXPECT_EQ(out.data, 42);

mqtt_client/CMakeLists.txt:74

• [nitpick] If you still need to skip the copyright check like before, add set(ament_cmake_copyright_FOUND TRUE) here to avoid breaking CI until all files have licenses.

set(ament_cmake_cpplint_FOUND TRUE)