debug: Add file listing to diagnose checkout issue

.github/workflows/deploy-book.yml

@@ -44,6 +44,17 @@ jobs:
         python-version: '3.11'
         cache: 'pip'
 
+    - name: Debug - List checked out files
+      run: |
+        echo "=== Root directory ==="
+        ls -la
+        echo "=== Book directory ==="
+        ls -la book/ || echo "book/ doesn't exist"
+        echo "=== Chapters directory ==="
+        ls -la book/chapters/ || echo "book/chapters/ doesn't exist"
+        echo "=== Git status ==="
+        git status
+        
     - name: Install dependencies
       run: |
         pip install --upgrade pip