chore(CMake): make Lts top-level resilient to partial checkouts and optional RTI/doxygen\n\n- Guard ADD_DOXYGEN_TARGET with existence check

- Add only existing Lts subdirectories to allow partial migrations
- Make RTI optional in Lts/Common/CodeGen and guard RTI target properties
\nCo-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Lts/CMakeLists.txt

@@ -7,19 +7,24 @@
 cmake_minimum_required(VERSION 3.16)
 project(LtsPlaceholder)
 SET(DOXYGEN_OUT_DIR ${CMAKE_CURRENT_BINARY_DIR}/doxygen_Lts)
-ADD_DOXYGEN_TARGET(Lts ${CMAKE_SOURCE_DIR}/doxygen/DoxyfileLts.in ${CMAKE_BINARY_DIR}/DoxyfileLts
-                           ${CMAKE_SOURCE_DIR}/doxygen/rheinmetall_defence_logo.jpg
-                                                      ${DOXYGEN_OUT_DIR})
+if (EXISTS "${CMAKE_SOURCE_DIR}/doxygen/DoxyfileLts.in")
+  ADD_DOXYGEN_TARGET(Lts ${CMAKE_SOURCE_DIR}/doxygen/DoxyfileLts.in ${CMAKE_BINARY_DIR}/DoxyfileLts
+                             ${CMAKE_SOURCE_DIR}/doxygen/rheinmetall_defence_logo.jpg
+                                                        ${DOXYGEN_OUT_DIR})
+else()
+  message(WARNING "Doxygen config ${CMAKE_SOURCE_DIR}/doxygen/DoxyfileLts.in not found; skipping ADD_DOXYGEN_TARGET(Lts)")
+endif()
 
-ADD_SUBDIRECTORY(Tools)
-ADD_SUBDIRECTORY(Application)
-ADD_SUBDIRECTORY(Common)
-ADD_SUBDIRECTORY(DDS)
-ADD_SUBDIRECTORY(Plugins)
-ADD_SUBDIRECTORY(Projects)
-ADD_SUBDIRECTORY(Proxies)
-ADD_SUBDIRECTORY(Services)
-ADD_SUBDIRECTORY(Viewer)
+# Add only existing subdirectories to allow partial checkouts / incremental migration
+set(LTS_SUBDIRS Tools Application Common DDS Plugins Projects Proxies Services Viewer)
+foreach(dir IN LISTS LTS_SUBDIRS)
+  if (EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/${dir}")
+    ADD_SUBDIRECTORY(${dir})
+  else()
+    message(STATUS "Skipping missing Lts subdirectory: ${dir}")
+  endif()
+
+endforeach()
 
 IF (BUILD_TESTING)
   ADD_SUBDIRECTORY(Tests)