What changed

• Add lychee-based docs link checking for changed/new .rst and .md links through pre-commit.
• Add a rendered-docs lychee CI workflow that runs after the docs build/deploy job.
• Have the docs build workflow publish the rendered HTML tree as an artifact for the downstream lychee workflow.
• Run rendered-docs lychee checks against the local generated HTML artifact instead of the deployed PR preview.
• Make docs example source links stable by using CUDA_PYTHON_DOCS_GITHUB_REF for release, preview, and latest builds.
• Apply stable source-link handling to cuda.bindings, cuda.core, cuda.pathfinder, and cuda-python docs.
• Clean up known broken docs links so lychee has a passing baseline.

Split

This PR is now only the docs link-checking and stable source-link work. Generated cuda.bindings pyobj-reference and pointer-rendering artifacts were split into #2167.

The earlier Sphinx linkcheck and check_example_links.py experiments were removed; lychee is the link checker for both local changed-link checks and rendered HTML checks.

Validation

• git diff --check origin/main...HEAD
• pixi run pre-commit run actionlint --files .github/workflows/build-docs.yml .github/workflows/check-doc-links.yml .github/workflows/ci.yml
• pixi run pre-commit run check-yaml --files .github/workflows/build-docs.yml .github/workflows/check-doc-links.yml .github/workflows/ci.yml
• Pre-commit hooks ran during the original commits, including lychee.
• Split verification: this PR only touches docs link checking/workflow/config/source docs files, not generated cuda.bindings Cython artifacts or generated pointer-rendering docs.