ci: publish documentation pages

[voltjia]

Summary

• Add .github/workflows/docs-pages.yml to build the Doxygen reference, validate the generated index.html, upload a Pages artifact, and deploy master builds with GitHub Pages.
• Build a CPU-only InfiniRT prefix inside the workflow before configuring InfiniOps documentation so INFINI_RT_ROOT is available.
• Update docs/README.md, docs/build.md, and docs/api/reference.md to describe PR validation and master publishing.

Motivation

InfiniOps now has a local Doxygen target, but documentation publishing still needs CI coverage. This PR mirrors the InfiniRT documentation Pages workflow while accounting for InfiniOps' InfiniRT dependency and wrapper-generation Python dependencies.

Closes N/A - staged documentation system follow-up.

Type of Change

• feat - new feature / new operator / new platform
• fix - bug fix
• perf - performance improvement (no behavioral change)
• refactor - code restructuring without behavior change
• test - adding or fixing tests only
• docs - documentation only
• build / ci - build system or CI configuration
• chore - tooling, formatting, or other non-code changes
• Breaking change (requires a ! in the Conventional Commits prefix or a BREAKING CHANGE: footer)

Platforms Affected

• CPU (WITH_CPU)
• NVIDIA (WITH_NVIDIA)
• Iluvatar (WITH_ILUVATAR)
• MetaX (WITH_METAX)
• Cambricon (WITH_CAMBRICON)
• Moore (WITH_MOORE)
• Ascend (WITH_ASCEND)
• PyTorch C++ bindings (WITH_TORCH)
• Build system / CMake / CI
• Python bindings / user-facing API

Smoke Test Result

git diff --check
# passed

rg -n "infinirt-prefix|[^\\x00-\\x7F]" .github/workflows/docs-pages.yml docs/api/reference.md docs/build.md docs/README.md
# no matches

gh run view 29082823001 --json event,conclusion,jobs
# Documentation Pages: event=pull_request, conclusion=success
# build job: success
# deploy job: skipped, as expected for non-master pull_request events
# successful build steps included:
# - Install documentation dependencies
# - Build InfiniRT
# - Configure documentation build
# - Build documentation
# - Validate generated site
# - Upload Pages artifact
# uploaded artifact: github-pages, 8268739 bytes, artifact ID 8223519973

The deploy job is intentionally gated by github.event_name == 'push' && github.ref == 'refs/heads/master', so PR validation exercises the build and artifact path without publishing Pages.

Test Results on Supported Platforms

Platform	Affected	Build / Smoke Result	Full Result / Notes
NVIDIA	No	N/A - not affected	N/A - CI workflow only
Iluvatar	No	N/A - not affected	N/A - CI workflow only
MetaX	No	N/A - not affected	N/A - CI workflow only
Cambricon	No	N/A - not affected	N/A - CI workflow only
Moore	No	N/A - not affected	N/A - CI workflow only
Ascend	No	N/A - not affected	N/A - CI workflow only

Full `pytest` output (optional)

N/A - no Python or operator code changed.

Benchmark / Performance Impact

N/A - CI and documentation publishing only.

Notes for Reviewers

The workflow deploys only on pushes to master; pull requests build the same infiniops_docs target and upload the generated HTML as a Pages artifact for validation. Repository Pages source must be configured to GitHub Actions before deployment can publish the site.