Clean up stale dirs before creating source copies

Self-hosted runners don't clean workspaces between runs, so config
directories from cancelled prior runs can persist. Add rm -rf before
cp -al/rsync to prevent "same file" hardlink errors when copying
into an existing directory.

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

Author: sbryngelson

.github/scripts/run_frontier_all_benchmarks.sh

@@ -31,6 +31,7 @@ for cfg in "${configs[@]}"; do
     read -r version cluster device interface <<< "$cfg"
     dir="${version}-${cluster}-${device}-${interface}"
     echo "Creating source copy: $dir from $version/"
+    rm -rf "$dir"
     cp -al "$version" "$dir" 2>/dev/null || cp -r "$version" "$dir"
 done
 

.github/scripts/run_frontier_all_tests.sh

@@ -36,6 +36,7 @@ for cfg in "${configs[@]}"; do
     read -r cluster device interface <<< "$cfg"
     dir="test-${cluster}-${device}-${interface}"
     echo "Creating source copy: $dir"
+    rm -rf "$dir"
     rsync -a --link-dest="$(pwd)" $excludes ./ "$dir/"
 done