Make the documentation build without CMake

[derobins]

docs/conf.py and the Doxygen configuration were templates that CMake filled in with configure_file(): the version, the Doxygen output directory, and Breathe's XML path. Run on their own, as Read the Docs runs them for rocm-systems projects, they didn't work. Both now work as committed, and the CMake build only sends their output to the build tree.

• docs/Doxyfile.in is now docs/doxygen/Doxyfile, with paths relative to docs/doxygen. Running doxygen there writes the XML to docs/doxygen/xml/, which .gitignore ignores. STRIP_FROM_PATH = ../.. keeps the XML's file names relative to the repository root (include/hipobj.h). PROJECT_NUMBER is gone, since nothing that Breathe renders uses it.
• docs/conf.py reads the version from the top-level CMakeLists.txt, and looks for the XML in doxygen/xml by default.
• HIPOBJDocumentation.cmake writes a Doxyfile in the build tree that @includes the committed one and changes only OUTPUT_DIRECTORY, and runs doxygen in docs/doxygen. It runs Sphinx on docs/ directly, and passes the XML's location in the build tree with -D breathe_projects.hipobj=..., so it no longer copies conf.py into the build tree.
• The documentation's Python requirements moved from the top-level requirements.txt to docs/sphinx/requirements.txt, where ROCm projects keep them. The requirements.txt entries in the workflows' path filters are gone, since docs/** covers the new location, and the documentation check and deploy workflows also run when the top-level CMakeLists.txt changes, since conf.py reads the version from it.

docs/building.rst describes the virtual environment and the build without CMake, AGENTS.md says to keep CMake substitutions out of both files, and CHANGELOG.md has an entry for the moves.

Testing: built the documentation before and after the change with a docs-only CMake configuration. The Doxygen XML is the same apart from its record of the configuration, and the HTML from clean builds is identical apart from Sphinx's .buildinfo file. Running doxygen in docs/doxygen and then sphinx-build -W on docs, without CMake, produces the same HTML. black, pylint, vermin, cmakelint, actionlint, doc8, and codespell are clean.

[github-actions]

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[Copilot]

🟢 Approval recommended

The configuration, path, and workflow changes are consistent, with no unresolved blocking findings.

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What changed in this PR

Makes hipObject’s documentation build without CMake, supporting the planned rocm-systems integration while preserving CMake builds.

Changes:

• Makes Doxygen and Sphinx configurations directly usable.
• Relocates Python requirements and updates workflow filters.
• Documents standalone builds and ignores generated XML.

File	Description
docs/​sphinx/​requirements.txt	Relocates documentation dependencies.
docs/​doxygen/​Doxyfile	Provides standalone Doxygen configuration.
docs/​conf.py	Reads the version and defaults to local XML.
docs/​building.rst	Documents standalone builds and virtual environments.
cmake/​HIPOBJDocumentation.cmake	Redirects documentation output without configuring source files.
CHANGELOG.md	Records configuration moves and standalone support.
AGENTS.md	Updates documentation-build guidance.
.gitignore	Ignores generated Doxygen XML.
.github/​workflows/​hipobject-iwyu.yml	Removes the obsolete requirements exclusion.
.github/​workflows/​hipobject-documentation-deploy.yml	Deploys documentation after version-source changes.
.github/​workflows/​hipobject-documentation-check.yml	Checks documentation after version-source changes.
.github/​workflows/​hipobject-clang-tidy.yml	Removes the obsolete requirements exclusion.
.github/​workflows/​hipobject-build.yml	Removes the obsolete requirements exclusion.
.github/​workflows/​codeql.yml	Removes the obsolete requirements exclusion.

_{Review effort: Balanced}