Remove aggressive workspace cleanup from test jobs

The rm -rf * was destroying the build cache, causing CMake to rebuild
from scratch and hit Lustre ioctl errors. With clean: false on
checkout, git clean is already disabled — no pre-cleanup needed.
Keep full cleanup only in bench.yml where pr/master are fresh clones.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: sbryngelson

.github/workflows/test.yml

@@ -222,16 +222,6 @@ jobs:
       ACTIONS_RUNNER_FORCE_ACTIONS_NODE_VERSION: node16
       ACTIONS_ALLOW_USE_UNSECURE_NODE_VERSION: true
     steps:
-      - name: Clean workspace (Lustre-safe)
-        shell: bash
-        run: |
-          shopt -s dotglob nullglob
-          for i in 1 2 3 4 5; do
-            rm -rf -- "${GITHUB_WORKSPACE:?}/"* 2>/dev/null && break
-            echo "Clean attempt $i failed, retrying in 2s..."
-            sleep 2
-          done
-
       - name: Clone
         uses: actions/checkout@v4
         with: