DOC: State the CMake 3.26 floor for Python wrapping

Development.SABIModule requires CMake >= 3.26. Builds without
ITK_WRAP_PYTHON keep the older floor.

Author: hjmjohnson

Documentation/docs/contributing/python_packaging.md

@@ -17,11 +17,15 @@ This section describes how to build Python packages for the main ITK libraries u
 ## Prerequisites
 
 Building ITK Python wheels requires the following:
-- CMake >= 3.16
+- CMake >= 3.26, for the `FindPython` `Development.SABIModule` component
 - Git
 - C++ Compiler (see [scikit-build platform specific requirements](https://scikit-build.readthedocs.io/en/latest/generators.html))
 - Python >= 3.11
 
+Wrapped modules are always built as stable-ABI (`abi3`) extensions, so a single
+set of wheels serves every supported Python version. Builds that do not set
+`ITK_WRAP_PYTHON=ON` are unaffected and still accept older CMake.
+
 ## Automated Platform Scripts
 
 The following sections outline how to use the ITKPythonPackage project to build wheels on Linux, macOS, and Windows. Each script will fetch tagged ITK sources, build ITK with Python wrappings, and package binaries into the Python wheel archive format for distribution.