fix: generate the site before CI runs the suite

docs/ is gitignored and was built after the tests, so the three guards
that read rendered pages skipped on every CI run. The site is generated
first, the suite runs whatever that step returns, and the guards fail
in CI when the pages are absent.

.github/workflows/validate.yml

@@ -231,7 +231,14 @@ jobs:
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
+      # docs/ is gitignored, and the tests that read the rendered pages fail
+      # in CI without it. The suite runs whatever this step returned, so a
+      # generator that stops still leaves every other test reporting.
+      - name: Generate the site
+        run: python scripts/generate_site.py
+
       - name: Run test suite
+        if: ${{ !cancelled() }}
         # No test downloads a release asset: 252 MB files fetched into the
         # shared cache filled the runner's disk and changed what later tests
         # resolved. The download tests mock the network and clear it.
@@ -246,7 +253,6 @@ jobs:
       - name: Build the site
         if: ${{ !cancelled() }}
         run: |
-          python scripts/generate_site.py
           mkdocs build --strict
           python scripts/validate_site.py