MRICloudCalculateDiffmap
========================

**Purpose.** Build 3D **control**, **label**, and **difference (control − label)**
maps by averaging over ASLContext volumes.

Inputs
------

- If ``data_descrip["SingleDelay"]``: uses ``derivatives/<sub>/perf/r{asl}.nii``
- Else (multi-delay): uses ``derivatives/<sub>/perf/{asl}.nii``
- Requires ``ASLContext`` entries (``"control"`` and ``"label"``).

Outputs
-------

- ``r{asl}_ctrl.nii`` — averaged control image (3D)
- ``r{asl}_labl.nii`` — averaged label image (3D)
- ``r{asl}_diff.nii`` — difference image (3D)

All saved to ``derivatives/<sub>/perf/``.

Configuration
-------------

- None.

YAML example
------------

.. code-block:: yaml

    modules:
      - name: MRICloudCalculateDiffmap