ci: skip cloud runner cleanup when disk headroom is ample (#13191)

Skip cloud runner disk cleanup when both the Docker and workspace filesystems have at least 64 GiB free. Preserve the existing cleanup for low, unavailable, or invalid measurements and verify the actual shell behavior across eight scenarios.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

.github/workflows/docker-cloud.yml

@@ -120,6 +120,18 @@ jobs:
           echo "Disk before cleanup:"
           df -h
 
+          # A measured hosted cloud build started with 86 GB available.
+          # Keep ample headroom for BuildKit and image verification, but
+          # avoid minutes deleting SDKs when neither filesystem needs space.
+          minimum_free_kib=$((64 * 1024 * 1024))
+          if docker_root="$(docker info --format '{{.DockerRootDir}}')" \
+            && available_kib="$(df -Pk "$docker_root" "$GITHUB_WORKSPACE" | awk 'NR > 1 { rows++; if ($4 !~ /^[0-9]+$/) invalid = 1; if (min == "" || $4 < min) min = $4 } END { if (invalid || rows != 2) exit 1; print min }')" \
+            && [[ "$available_kib" =~ ^[0-9]+$ ]] \
+            && (( available_kib >= minimum_free_kib )); then
+            echo "At least 64 GiB is available for Docker and the workspace; skipping cleanup."
+            exit 0
+          fi
+
           pnpm store prune || true
           sudo apt-get clean || true
           sudo rm -rf \