👷 ci(docs): add MkDocs Pages workflow (E5-S04)

.github/workflows/docs.yaml

@@ -0,0 +1,80 @@
+# MkDocs Material site: strict build on every docs change; deploy from main only.
+# Pages source is workflow (OD-5). Release tags never deploy — push is main-only.
+name: Docs
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - "docs/**"
+      - "mkdocs.yml"
+      - "README.md"
+      - ".github/workflows/docs.yaml"
+  pull_request:
+    paths:
+      - "docs/**"
+      - "mkdocs.yml"
+      - "README.md"
+      - ".github/workflows/docs.yaml"
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: docs-${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
+jobs:
+  build:
+    name: Build MkDocs site
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    permissions:
+      contents: read
+    steps:
+      - name: Checkout
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+
+      - name: Set up Python
+        uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97 # v7.0.0
+        with:
+          python-version: "3.12"
+          cache: pip
+          cache-dependency-path: docs/requirements-docs.txt
+
+      - name: Install MkDocs Material
+        run: |
+          pip install --only-binary=:all: --require-hashes -r docs/requirements-docs.txt
+
+      - name: Build site
+        run: mkdocs build --strict
+
+      - name: Upload Pages artifact
+        uses: actions/upload-pages-artifact@fc324d3547104276b827a68afc52ff2a11cc49c9 # v5.0.0
+        with:
+          path: site
+
+  deploy:
+    name: Deploy to GitHub Pages
+    if: github.event_name != 'pull_request'
+    needs: build
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    concurrency:
+      group: pages
+      cancel-in-progress: false
+    permissions:
+      pages: write
+      id-token: write
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - name: Deploy
+        id: deployment
+        uses: actions/deploy-pages@cd2ce8fcbc39b97be8ca5fce6e763baed58fa128 # v5.0.0