Add Lustre-safe workspace cleanup for self-hosted runners

Disable actions/checkout's built-in git clean (which fails on Lustre
with ESTALE/ENOTEMPTY errors) and add a retry-based rm -rf step before
checkout instead.

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

Author: sbryngelson

.github/workflows/bench.yml

@@ -90,14 +90,25 @@ jobs:
       ACTIONS_RUNNER_FORCE_ACTIONS_NODE_VERSION: node16
       ACTIONS_ALLOW_USE_UNSECURE_NODE_VERSION: true
     steps:
+      - name: Clean workspace (Lustre-safe)
+        run: |
+          for i in 1 2 3 4 5; do
+            rm -rf "$GITHUB_WORKSPACE"/pr "$GITHUB_WORKSPACE"/master 2>/dev/null && break
+            echo "Clean attempt $i failed, retrying in 2s..."
+            sleep 2
+          done
+          true
+
       - name: Clone - PR
         uses: actions/checkout@v4
         with:
+          clean: false
           path: pr
 
       - name: Clone - Master
         uses: actions/checkout@v4
         with:
+          clean: false
           repository: MFlowCode/MFC
           ref: master
           path: master

.github/workflows/test.yml

@@ -219,8 +219,19 @@ jobs:
       ACTIONS_RUNNER_FORCE_ACTIONS_NODE_VERSION: node16
       ACTIONS_ALLOW_USE_UNSECURE_NODE_VERSION: true
     steps:
+      - name: Clean workspace (Lustre-safe)
+        run: |
+          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
+          true
+
       - name: Clone
         uses: actions/checkout@v4
+        with:
+          clean: false
 
       - name: Build
         if:   matrix.cluster != 'phoenix'