Implement text-on-path rendering

[jremillard]

Summary

• add static TextOnPath helper with new and legacy algorithms
• use TextOnPath::drawTextOnPath in RenderQT
• extend textonpath_test to use the new class
• regenerate coverage report
• correct rotation logic in drawTextOnPath to keep labels upright

Testing

• cmake -S . -B bin/release -DCMAKE_BUILD_TYPE=Release
• cmake -S . -B bin/debug -DCMAKE_BUILD_TYPE=Debug
• cmake -S . -B bin/coverage -DOSMMAPMAKER_ENABLE_COVERAGE=ON
• cmake -S . -B bin/valgrind -DOSMMAPMAKER_ENABLE_VALGRIND=ON
• cmake --build bin/release -j$(nproc)
• cmake --build bin/debug -j$(nproc)
• cmake --build bin/coverage -j$(nproc)
• cmake --build bin/valgrind -j$(nproc)
• ctest --test-dir bin/release
• ctest --test-dir bin/valgrind
• ctest --output-on-failure --test-dir bin/release
• ctest --output-on-failure --test-dir bin/valgrind
• valgrind --tool=memcheck --suppressions=valgrind.supp bin/valgrind/tests/hello_test
• valgrind --tool=helgrind --suppressions=valgrind.supp bin/valgrind/tests/hello_test
• ctest --output-on-failure --test-dir bin/coverage
• lcov --capture --directory bin/coverage --output-file bin/coverage/coverage.info
• lcov --remove bin/coverage/coverage.info '/usr/*' '*/tests/*' --output-file bin/coverage/coverage.info
• lcov --list bin/coverage/coverage.info | sort -k2 > tests/coverage_report.txt

---

https://chatgpt.com/codex/tasks/task_e_6868b42dfc40833082acbb7918e7f52e