github: Add docs artifact upload step to CI for pull requests

- Updated `.github/workflows/test-and-publish.yml` to add a step for uploading
  documentation preview artifacts when triggered by pull requests.
- Artifacts are retained for 7 days to aid in documentation review and testing.

Assisted-by: Codex

Author: datalogics-kam

.github/workflows/test-and-publish.yml

@@ -29,6 +29,13 @@ jobs:
         run: uv sync --group dev
       - name: Build docs with MkDocs
         run: uv run mkdocs build --strict
+      - name: Upload docs preview artifact
+        if: github.event_name == 'pull_request'
+        uses: actions/upload-artifact@v4
+        with:
+          name: docs-site
+          path: site/
+          retention-days: 7
 
   tests:
     name: Tests (Python ${{ matrix.python-version }})