workflows: docs: add

Create a custom workflow for deploying our documentation to GitHub
Pages. This allows us to retain the original YAML-to-documentation
generation process we've used in the past, and stops us from relying
solely on files already being on the main branch for documentation build
and review.

We have to incorporate two new community actions for this:

1. `peaceiris/actions-gh-pages`, for deploying the actual docs using a
   `gh-pages` branch
2. `rossjrew/pr-preview-action`, for creating docs previews so we're
   able to review the changes before merge. Comments will be posted on
   the PR providing preview links.

The `gh-pages` branch also requires a `.nojekyll` file at the project
root to avoid a manual rebuild, which can take a lot of time. Finally,
the `Deploy from a branch` option in the Pages setting needs to point at
`root/`, not `docs/` or it won't find the `.nojekyll` file.

AI-Generated: Uses Claude Sonnet 5

Signed-off-by: Trevor Gamblin <tgamblin@baylibre.com>

Author: threexc

.github/workflows/docs.yml

@@ -0,0 +1,113 @@
+# SPDX-FileCopyrightText: 2026 The RISE Project
+# SPDX-License-Identifier: MIT
+
+name: Build and deploy documentation
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - "docs/**"
+  pull_request:
+    types: [opened, synchronize, reopened, closed]
+  workflow_dispatch:
+
+concurrency:
+  group: docs-${{ github.ref }}
+
+jobs:
+  preview:
+    if: github.event_name == 'pull_request'
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      pull-requests: write
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-python@v5
+        if: github.event.action != 'closed'
+        with:
+          python-version: '3'
+
+      - name: Install package doc generator dependencies
+        if: github.event.action != 'closed'
+        run: pip install -r docs/requirements.txt
+
+      - name: Generate package pages from YAML
+        if: github.event.action != 'closed'
+        run: python docs/packages/generate_packages_doc.py
+
+      - name: Compute preview baseurl
+        if: github.event.action != 'closed'
+        id: preview_baseurl
+        run: |
+          base=$(python3 -c "import yaml; print(yaml.safe_load(open('docs/_config.yml'))['baseurl'])")
+          echo "value=${base}/pr-preview/pr-${{ github.event.number }}" >> "$GITHUB_OUTPUT"
+
+      - uses: ruby/setup-ruby@v1
+        if: github.event.action != 'closed'
+        with:
+          ruby-version: '3.3'
+
+      # actions/jekyll-build-pages has no way to override _config.yml's
+      # hardcoded baseurl, but a preview is served one path segment deeper
+      # (.../pr-preview/pr-<N>/) than the production site, so it needs its
+      # own baseurl or every internal link/asset would point at production.
+      - name: Build with Jekyll
+        if: github.event.action != 'closed'
+        run: |
+          # jekyll-remote-theme only fetches just-the-docs' layouts/assets;
+          # its own gem dependencies (jekyll-seo-tag, jekyll-include-cache,
+          # rake) still have to be installed separately.
+          gem install jekyll jekyll-remote-theme jekyll-seo-tag jekyll-include-cache rake --no-document
+          jekyll build --source docs --destination _site \
+            --baseurl "${{ steps.preview_baseurl.outputs.value }}"
+
+      # Auto-detects deploy vs. removal from the pull_request event action,
+      # so this same step both publishes updates and tears down the preview
+      # when the PR is closed.
+      #
+      # wait-for-pages-deployment is deliberately left at its default
+      # (false): on classic "deploy from a branch" Pages, its lookup against
+      # the legacy Pages Builds API doesn't reliably find an exact-commit
+      # build within its hardcoded 180s timeout, and that timeout is a hard,
+      # non-configurable `exit 1` that fails the whole step/PR check even
+      # when the preview deployed and is serving correctly. A link that's
+      # occasionally not live for a few seconds is a smaller problem than a
+      # misleading red X on an otherwise-working PR.
+      - name: Deploy or remove PR preview
+        uses: rossjrw/pr-preview-action@v1
+        with:
+          source-dir: ./_site
+
+  deploy:
+    if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3'
+
+      - name: Install package doc generator dependencies
+        run: pip install -r docs/requirements.txt
+
+      - name: Generate package pages from YAML
+        run: python docs/packages/generate_packages_doc.py
+
+      - name: Build with Jekyll
+        uses: actions/jekyll-build-pages@v1
+        with:
+          source: ./docs
+          destination: ./_site
+
+      - name: Deploy to GitHub Pages
+        uses: peaceiris/actions-gh-pages@v4
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: ./_site
+          keep_files: true