ci(tests[builder]): Switch docs CI check to dirhtml to match deploy

why: CI should validate the same builder format that gets deployed;
     keeps tests.yml and docs.yml in sync
what:
- Change sphinx-build -b html to -b dirhtml in tests docs job

Author: tony

.github/workflows/tests.yml

@@ -79,7 +79,7 @@ jobs:
         run: uv sync --all-packages --all-extras --group dev
 
       - name: Build documentation with warnings as errors
-        run: uv run sphinx-build -W -b html docs docs/_build/html
+        run: uv run sphinx-build -W -b dirhtml docs docs/_build/html
 
   packages:
     runs-on: ubuntu-latest