project outline doesn't show header files if grpc src (.cc) is added

### Brief Issue Summary

in cmakelist.txt when you want to add an executable you simple write
`add_executable(${PROJECT_NAME}_exe ${SOURCES} ${HEADERS} )`
this will make sure that the project outline view will show the executable with the sources and header files


however ...
if you try to add grpc source files ( filename.grpc.pb.cc) like so:

`add_executable(${PROJECT_NAME}_exe ${SOURCES} ${HEADERS} ${GRPC_SRCS})`

now the project outline removes any header file and create a new entry name build/proto-src


header files are shown properly in any other ide, so this has to be an issue, right ?

### CMake Tools Diagnostics

_No response_

### Debug Log

_No response_

### Additional Information

_No response_

Start with the CMakeLists.txt example using add_executable and compare the project outline when ${GRPC_SRCS} includes a .grpc.pb.cc file. Trace how the outline handles generated sources and header files, then reproduce the reported build/proto-src entry. Done means the executable retains its header files in the outline without the incorrect grouping.

Written by the indexing model from the issue text.