Add tests/CMakeLists.txt to include benchmark tests

- Links qt6-migrated-benchmark/tests into main test suite
- Enables CTest discovery of migration tests

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

qt6-after/qt6-migrated-legatus/tests/CMakeLists.txt

@@ -0,0 +1,11 @@
+# Root tests CMakeLists.txt
+# Includes all test subdirectories
+
+# Include migration benchmark tests
+if(EXISTS "${CMAKE_SOURCE_DIR}/../qt6-migrated-benchmark/tests/CMakeLists.txt")
+    add_subdirectory(${CMAKE_SOURCE_DIR}/../qt6-migrated-benchmark/tests migration_benchmark_tests)
+endif()
+
+# Include other test directories as they become available
+# add_subdirectory(gtest)
+# add_subdirectory(strix)