COMP: Fix missing include path and nodiscard warning

Add the module's include/ directory to the src/ executables' include
path so that itkVariationalRegistrationMultiResolutionFilter.h and
other module headers are found during the CTest dashboard build.

Also fix the nodiscard warning on TransformPhysicalPointToContinuousIndex
in itkContinuousBorderWarpImageFilter.hxx by throwing an exception when
the physical point falls outside the image domain.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hjmjohnson

include/itkContinuousBorderWarpImageFilter.hxx

@@ -72,7 +72,10 @@ ContinuousBorderWarpImageFilter<TInputImage, TOutputImage, TDisplacementField>::
       }
 
       // project point into image region
-      inputPtr->TransformPhysicalPointToContinuousIndex(point, contIndex);
+      if (!inputPtr->TransformPhysicalPointToContinuousIndex(point, contIndex))
+      {
+        itkExceptionMacro("Physical point " << point << " is outside the image domain");
+      }
 
       for (unsigned int j = 0; j < ImageDimension; j++)
       {

src/CMakeLists.txt

@@ -1,3 +1,4 @@
+include_directories("${VariationalRegistration_SOURCE_DIR}/include")
 include_directories("${VariationalRegistration_SOURCE_DIR}/src")
 
 # Test if ITK is built with FFTW. FFTWD is recommended and required for the