DOC: Add MultipleImageIterator README and clean module scaffolding

- Add README pointing at archived upstream.
- Replace upstream COMPILE_DEPENDS with DEPENDS ITKCommon (header-only template).
- Inline DESCRIPTION instead of multi-line set(DOCUMENTATION).
- Add \ingroup ImageIterators topical tag.

Author: hjmjohnson

Modules/Core/MultipleImageIterator/README.md

@@ -0,0 +1,24 @@
+# MultipleImageIterator
+
+In-tree ITK module providing `itk::MultipleImageIterator`, a single
+iterator that walks any number of co-registered images in lockstep.
+The iterator returns a `std::vector` of pixel values (or references)
+at each position, simplifying multi-channel processing without the
+boilerplate of synchronizing N separate iterators.
+
+## Origin
+
+Ingested from the standalone remote module
+[**KitwareMedical/MultipleImageIterator**](https://github.com/KitwareMedical/MultipleImageIterator)
+on 2026-05-12, following the v4 ingestion guidelines defined in
+InsightSoftwareConsortium/ITK#6204. Placed under `Modules/Core/` to
+match the placement of other ITK iterators (`itkImageRegionIterator`,
+`itkNeighborhoodIterator`). The upstream repository will be archived
+read-only after this PR merges; it remains reachable at the URL above
+for historical reference.
+
+## References
+
+- Schaerer J. *A MultipleImageIterator for iterating over multiple
+  images simultaneously.* The Insight Journal. December 2014.
+  <https://doi.org/10.54294/e5lmyz>

Modules/Core/MultipleImageIterator/include/itkMultipleImageIterator.h

@@ -29,6 +29,7 @@ namespace itk
  * All iterators must
  *  - point to images of the same type
  *  - be of the same size (number of values from begin to end)
+ * \ingroup ImageIterators
  * \ingroup MultipleImageIterator */
 template <typename TIterator>
 class MultipleImageIterator

Modules/Core/MultipleImageIterator/itk-module.cmake

@@ -1,28 +1,11 @@
-set(
-  DOCUMENTATION
-  "Several applications such as multi-atlas segmentation
-require frequent iteration over multiple image volumes at the same time.
-Doing so with the regular ITK iterators is tedious and error prone
-as it requires updating each iterator at end of each iteration.
-Failing to do so results in hard to debug errors and crashes.
-The MultipleImageIterator is a simple wrapper class that tries to make this more convenient.
-
-A more detailed description can be found in the Insight Journal article::
-Schaerer J. \"A MultipleImageIterator for iterating over multiple images simultaneously\".
-  https://hdl.handle.net/10380/3455
-  https://www.insight-journal.org/browse/publication/915
-  December, 2014.
-"
-)
-
+# Maintainer: Joel Schaerer
 itk_module(
   MultipleImageIterator
-  # DEPENDS
-  # ITKCommon
-  COMPILE_DEPENDS
+  DEPENDS
     ITKCommon
   TEST_DEPENDS
     ITKTestKernel
   EXCLUDE_FROM_DEFAULT
-  DESCRIPTION "${DOCUMENTATION}"
+  DESCRIPTION
+    "An iterator wrapper that walks multiple co-registered images in lockstep, returning a std::vector of pixel values at each position. https://doi.org/10.54294/e5lmyz"
 )