Deploy docs from the docs branch (not main) via gh-pages

Trigger the workflow on push to the docs branch instead of main, and
switch from the GitHub Actions Pages artifact path to mkdocs' built-in
gh-deploy command — which builds the site and force-pushes the result
to a gh-pages branch.

This keeps the docs source-of-truth on its own branch, with main
completely untouched. The gh-pages branch is auto-managed; do not edit
it directly.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hua7450

.github/workflows/docs.yml

@@ -2,27 +2,27 @@ name: Build and deploy docs
 
 on:
   push:
-    branches: [main]
+    branches: [docs]
     paths:
       - "docs/**"
       - "mkdocs.yml"
       - ".github/workflows/docs.yml"
   workflow_dispatch:
 
 permissions:
-  contents: read
-  pages: write
-  id-token: write
+  contents: write   # needed to push the built site to the gh-pages branch
 
 concurrency:
-  group: pages
+  group: docs
   cancel-in-progress: false
 
 jobs:
-  build:
+  deploy:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0   # gh-deploy needs full history to update gh-pages
 
       - uses: actions/setup-python@v5
         with:
@@ -31,19 +31,10 @@ jobs:
       - name: Install MkDocs
         run: pip install mkdocs-material==9.5.34
 
-      - name: Build site
-        run: mkdocs build --strict
-
-      - uses: actions/upload-pages-artifact@v3
-        with:
-          path: site
+      - name: Configure git identity
+        run: |
+          git config user.name "github-actions[bot]"
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
 
-  deploy:
-    needs: build
-    runs-on: ubuntu-latest
-    environment:
-      name: github-pages
-      url: ${{ steps.deployment.outputs.page_url }}
-    steps:
-      - id: deployment
-        uses: actions/deploy-pages@v4
+      - name: Build and push to gh-pages
+        run: mkdocs gh-deploy --force