Fix CI: reduce xdist workers and fetch full git history

- Reduce PYTEST_XDIST_AUTO_NUM_WORKERS from 8 to 4 for style-and-cicd-tests
  to prevent OOM errors with Spark tests on GHA runners
- Add fetch-depth: 0 to style-and-cicd-tests checkout so setuptools_scm
  can resolve the version from git tags (fixes test_version_schema failure)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: eakmanrq <6326532+eakmanrq@users.noreply.github.com>

Author: eakmanrq

.github/workflows/pr.yaml

@@ -76,10 +76,12 @@ jobs:
       matrix:
         python-version: ['3.9', '3.10', '3.11', '3.12', '3.13']
     env:
-      PYTEST_XDIST_AUTO_NUM_WORKERS: 8
+      PYTEST_XDIST_AUTO_NUM_WORKERS: 4
       UV: '1'
     steps:
       - uses: actions/checkout@v5
+        with:
+          fetch-depth: 0
       - name: Set up Python
         uses: actions/setup-python@v6
         with: