[dylanjm]

Closes #67

Summary

Adds .github/workflows/docs.yml, which publishes the Sphinx docs to https://idaholabresearch.github.io/DCAF/ whenever a GitHub release is published (nothing runs on pushes or PRs).

• build: checks out the release tag, runs uv sync --locked, builds the docs with sphinx-build -b html docs docs/_build/html, and uploads the HTML with actions/upload-pages-artifact@v5.
• deploy: publishes the artifact with actions/deploy-pages@v5 to the github-pages environment.
• Permissions are least-privilege: contents: read for the workflow, and pages: write + id-token: write only on the deploy job. A single pages concurrency group stops two deploys from running at once.

Required one-time setup (repo admin)

1. Settings → Pages → Build and deployment → Source: "GitHub Actions". Until this is set, the deploy job fails with "Pages site not found".
2. Settings → Environments → github-pages → Deployment branches and tags: add a tag rule matching the release tags (e.g. v*). This environment is created when step 1 is done and only allows the default branch at first. Release runs come from the tag ref, so without this rule the deploy is rejected with "Tag ... is not allowed to deploy to github-pages due to environment protection rules".

Test plan

• sphinx-build -b html docs <out> succeeds locally (4 existing, non-fatal warnings: the missing _static dir and the unknown mermaid Pygments lexer)
• pre-commit run --all-files passes
• After merge and setup: publishing a release runs the Docs workflow and the site loads

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