FastSurfer-CC bugfixes

[ClePol]

This PR fixes multiple bugs in the corpus callosum module.

One critical bug was in the AC/PC localization, where the AC/PC was never correctly placed on the midslice.

Other bugs are mainly related to visualization and alternate subdivision schemes (not run in the default run_fastsurfer.sh configuration).

[Copilot]

Pull request overview

This PR fixes multiple bugs in the FastSurfer corpus callosum (CC) module, with a focus on AC/PC localization and visualization issues.

• Critical fix: AC/PC coordinates are now correctly placed on the midslice by converting physical coordinates to voxel coordinates (dividing FSAVERAGE_MIDDLE by voxel size)
• Critical fix: Midslice identification for QC image generation now uses loop counter instead of slice index
• Refactored subdivision tracking to directly store subdivision lines instead of retrospectively extracting them from contours

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
doc/overview/modules/CC.md	Clarifies that anatomical landmarks use LIA voxel coordinates and references orig.mgz space
CorpusCallosum/utils/visualization.py	Refactors plot functions with explicit view configurations, fixes reference contour selection, removes redundant plt.show()
CorpusCallosum/utils/types.py	Adds subdivision_lines field to CCMeasuresDict type definition
CorpusCallosum/shape/subsegment_contour.py	Standardizes subdivision functions to return and track subdivision_lines explicitly, ensures consistent A-to-P ordering, removes deprecated get_unique_contour_points function
CorpusCallosum/shape/postprocessing.py	Fixes midslice detection bug, updates make_subdivision_mask to use subdivision_lines directly, removes CCMesh from return values
CorpusCallosum/shape/curvature.py	Removes unused split_contours parameter from calculate_curvature_metrics
CorpusCallosum/fastsurfer_cc.py	Fixes AC/PC coordinate calculation by converting FSAVERAGE_MIDDLE to voxel space, updates function call to match new 3-value return

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[dkuegler]

Minor changes.