ENH: Default pixi build to latest ITK main; add pinned release-v6 track

The default pixi `build` task now configures the SuperBuild with
ITK_GIT_TAG=main so the guide is built and validated against current
ITK upstream/main, keeping documentation in step with the development
tree.

Add a parallel `configure-release-v6` / `build-release-v6` task pair
pinned to the v6.0b02 release tag, building in a separate
build-release-v6/ tree so the two tracks never clobber each other.

Author: hjmjohnson

pyproject.toml

@@ -31,25 +31,48 @@ ghostscript = ">=9.54"
 imagemagick = ">=7"
 pygments = ">=2.15"
 
+# Default track: build against the very latest ITK upstream/main, so the guide
+# documents current ITK. ITK_GIT_TAG flows into External_ITK.cmake's
+# ExternalProject_Add GIT_TAG.
 [tool.pixi.feature.dev.tasks.configure]
 cmd = '''cmake \
   -Bbuild \
   -S. \
   -GNinja \
   -DCMAKE_BUILD_TYPE:STRING=MinSizeRel \
+  -DITK_GIT_TAG:STRING=main \
   -DCMAKE_C_COMPILER_LAUNCHER:STRING=ccache \
   -DCMAKE_CXX_COMPILER_LAUNCHER:STRING=ccache'''
-description = "Configure the ITK Software Guide SuperBuild (builds ITK in Phase I)"
+description = "Configure the SuperBuild against the latest ITK upstream/main (builds ITK in Phase I)"
 outputs = ["build/CMakeFiles/"]
 
 [tool.pixi.feature.dev.tasks.build]
 # CCACHE_BASE_DIR = the SuperBuild tree (build/), covering both the ITK source
 # (build/ITK) and its build (build/ITK-build); ccache rewrites absolute paths
 # under it to relative, so cache hits survive repo relocation.
 cmd = '''CCACHE_BASE_DIR="$PWD/build" cmake --build build'''
-description = "Build the ITK Software Guide; PDFs land in build/ITKSoftwareGuide-build/SoftwareGuide/Latex/"
+description = "Build the ITK Software Guide against latest ITK main; PDFs land in build/ITKSoftwareGuide-build/SoftwareGuide/Latex/"
 depends-on = ["configure"]
 
+# Pinned-release track: build against a fixed ITK release tag in a separate
+# tree (build-release-v6/) so it never clobbers the default main build.
+[tool.pixi.feature.dev.tasks.configure-release-v6]
+cmd = '''cmake \
+  -Bbuild-release-v6 \
+  -S. \
+  -GNinja \
+  -DCMAKE_BUILD_TYPE:STRING=MinSizeRel \
+  -DITK_GIT_TAG:STRING=v6.0b02 \
+  -DCMAKE_C_COMPILER_LAUNCHER:STRING=ccache \
+  -DCMAKE_CXX_COMPILER_LAUNCHER:STRING=ccache'''
+description = "Configure the SuperBuild against the pinned ITK v6.0b02 release tag"
+outputs = ["build-release-v6/CMakeFiles/"]
+
+[tool.pixi.feature.dev.tasks.build-release-v6]
+cmd = '''CCACHE_BASE_DIR="$PWD/build-release-v6" cmake --build build-release-v6'''
+description = "Build the ITK Software Guide against the pinned ITK v6.0b02 release; PDFs land in build-release-v6/ITKSoftwareGuide-build/SoftwareGuide/Latex/"
+depends-on = ["configure-release-v6"]
+
 [tool.pixi.environments]
 build = ["dev", "latex"]
 pre-commit = ["pre-commit"]