Fix docs pr-preview to match standard build

Author: dalito

.github/workflows/test_pages_build.yaml

@@ -32,6 +32,12 @@ jobs:
         with:
           fetch-depth: 0
 
+      # https://github.com/actions/setup-python
+      - name: Set up Python 3
+        uses: actions/setup-python@v6.0.0
+        with:
+          python-version: 3.13
+
       # https://github.com/astral-sh/setup-uv
       - name: Install uv
         uses: astral-sh/setup-uv@v7.1.2
@@ -40,23 +46,22 @@ jobs:
           enable-cache: true
           cache-dependency-glob: "uv.lock"
 
-      # https://github.com/actions/setup-python
-      - name: Set up Python 3
-        uses: actions/setup-python@v6.0.0
-        with:
-          python-version: 3.13
+      - name: Install just
+        run: |
+          uv tool install rust-just
 
       - name: Install dependencies
         run: uv sync --dev --no-progress
 
       - name: Build documentation
         run: |
+          just gen-doc
           uv run mkdocs build -d site
           touch site/.nojekyll
 
       # https://github.com/rossjrw/pr-preview-action
       - name: Deploy preview
         uses: rossjrw/pr-preview-action@v1.6.2
         with:
-          source-dir: site/
+          source-dir: docs/
           preview-branch: gh-pages