Use this skill whenever the user wants to process structural MRI (sMRI) such as T1w/T2w/FLAIR for brain extraction, bias correction, tissue segmentation (GM/WM/CSF), registration to MNI, cortical/subcortical parcellation, cortical thickness/volumetry (FreeSurfer), HCP-style structural preprocessing, WMH lesion segmentation (FLAIR+T1), ROI-wise feature extraction, or converting results back to DICOM. This is the NeuroClaw modality-layer interface: it plans WHAT to do and delegates execution to tool skills.