ci: add GitHub Actions workflow to deploy Docusaurus to GitHub Pages

Triggers on push to main (course-content/** changes) or manual dispatch.
Build: Node 20, npm ci, docusaurus build.
Deploy: actions/deploy-pages with pages environment.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: initcron

.github/workflows/deploy-docs.yml

@@ -0,0 +1,55 @@
+name: Deploy Docusaurus to GitHub Pages
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - 'course-content/**'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: pages
+  cancel-in-progress: false
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: course-content
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: npm
+          cache-dependency-path: course-content/package-lock.json
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Build
+        run: npm run build
+
+      - uses: actions/configure-pages@v5
+
+      - uses: actions/upload-pages-artifact@v3
+        with:
+          path: course-content/build
+
+  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