ci: build docs in strict mode on PRs/pushes

Add a docs job that runs `mkdocs build --strict` so broken links or missing
pages fail CI on dev/main PRs. Deployment to GitHub Pages stays in docs.yml
(main only).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: vinisalazar

.github/workflows/python-app.yml

@@ -61,3 +61,19 @@ jobs:
         python -m pip install -e ".[dev,xarray]"
     - name: Run integration tests
       run: python -m pytest -m integration tests/
+
+  docs:
+    # Build the documentation in strict mode so broken links or missing pages
+    # fail the PR. Deployment to GitHub Pages stays in docs.yml (main only).
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - uses: actions/setup-python@v5
+      with:
+        python-version: "3.12"
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        python -m pip install -e ".[docs]"
+    - name: Build docs (strict)
+      run: mkdocs build --strict