[ci optional] fortitude lint, full test

Author: Debraheem

colors/private/colors_utils.f90

@@ -566,7 +566,7 @@ end subroutine read_strings_from_file
    ! so a stale or truncated cube reports a clear message instead of failing
    ! later inside the Fortran runtime.
    subroutine load_flux_cube(rq, stellar_model_dir)
-      use iso_fortran_env, only: int64
+      use, intrinsic :: iso_fortran_env, only: int64
       type(Colors_General_Info), intent(inout) :: rq
       character(len=*), intent(in) :: stellar_model_dir