COMP: Disable CI builds that require OpenSlide library

The CXX and Python wheel builds require the OpenSlide library
(https://openslide.org) which is not available on standard GitHub
Actions runners or in the dockcross manylinux containers used by
ITKRemoteModuleBuildTestPackageAction. These builds have never
passed in CI.

Disable the reusable workflow jobs and add a placeholder job that
documents the situation. The clang-format linter still runs. Local
build instructions are included in the workflow file comments.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hjmjohnson

.github/workflows/build-test-package.yml

@@ -10,11 +10,49 @@ on:
     branches:
       - main
 
-jobs:
-  cxx-build-workflow:
-    uses: InsightSoftwareConsortium/ITKRemoteModuleBuildTestPackageAction/.github/workflows/build-test-cxx.yml@v5.4.2
+# NOTE: The standard ITKRemoteModuleBuildTestPackageAction reusable
+# workflows are disabled because this module requires the OpenSlide
+# library (https://openslide.org) which is not available on the
+# GitHub Actions runners or in the dockcross manylinux containers.
+#
+# The clang-format linter (clang-format-linter.yml) still runs and
+# does not require OpenSlide.
+#
+# To build and test this module locally:
+#
+#   # Install OpenSlide (Ubuntu/Debian)
+#   sudo apt-get install libopenslide-dev
+#
+#   # Install OpenSlide (macOS)
+#   brew install openslide
+#
+#   # Configure and build against an existing ITK build
+#   cmake -S . -B build \
+#     -DCMAKE_BUILD_TYPE=Release \
+#     -DBUILD_TESTING=ON \
+#     -DITK_DIR=/path/to/ITK-build
+#   cmake --build build
+#   ctest --test-dir build
+
+# jobs:
+#   cxx-build-workflow:
+#     uses: InsightSoftwareConsortium/ITKRemoteModuleBuildTestPackageAction/.github/workflows/build-test-cxx.yml@v5.4.6
+#
+#   python-build-workflow:
+#     uses: InsightSoftwareConsortium/ITKRemoteModuleBuildTestPackageAction/.github/workflows/build-test-package-python.yml@v5.4.6
+#     with:
+#       itk-wheel-tag: 'v5.4.5'
+#       itk-python-package-tag: 'v5.4.5'
+#     secrets:
+#       pypi_password: ${{ secrets.pypi_password }}
 
-  python-build-workflow:
-    uses: InsightSoftwareConsortium/ITKRemoteModuleBuildTestPackageAction/.github/workflows/build-test-package-python.yml@v5.4.2
-    secrets:
-      pypi_password: ${{ secrets.pypi_password }}
+jobs:
+  placeholder:
+    runs-on: ubuntu-latest
+    steps:
+      - run: |
+          echo "Build and test workflows are disabled for this module."
+          echo "This module requires the OpenSlide library (https://openslide.org)"
+          echo "which is not available on standard GitHub Actions runners."
+          echo ""
+          echo "See .github/workflows/build-test-package.yml for local build instructions."