feat: add CI workflow for manuscript build validation

.gitea/workflows/validate.yml

@@ -0,0 +1,22 @@
+name: Build Validation
+
+on:
+  pull_request:
+    branches: [main]
+
+jobs:
+  validate-manuscript:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      
+      - name: Setup Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.x'
+          
+      - name: Run Chapter Validation
+        run: |
+          # Run the build script with --md flag which triggers validation
+          # If validation fails, the script exits with code 1, failing the CI
+          python3 build/build.py --md