fix(ci): ride out transient network flakes instead of failing the run

.github/workflows/ci.yml

@@ -63,6 +63,9 @@ jobs:
     runs-on: ubuntu-latest
     env:
       BUNDLE_GEMFILE: ${{ github.workspace }}/${{ matrix.gemfile }}
+      # Every job resolves from scratch (Gemfile.lock is removed below), so one
+      # rubygems.org blip fails the whole job - give bundler extra retries.
+      BUNDLE_RETRY: "6"
     steps:
       - uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
         with:
@@ -102,4 +105,7 @@ jobs:
         if: always()
         run: |
           df -h
-          sudo du -sh /mnt/docker
+          # /mnt/docker only exists if the Docker configure step ran; without the
+          # guard this always() step adds a second, misleading failure whenever an
+          # earlier step (e.g. bundle install) is what actually failed.
+          if [ -d /mnt/docker ]; then sudo du -sh /mnt/docker; fi

test/integration/integration_test.rb

@@ -193,9 +193,21 @@ def compose_up_with_retry
       retry
     end
 
+    # Base-image pulls go straight to Docker Hub from the host daemon, so a Hub
+    # blip fails the build for this test and every one after it ($IMAGES_BUILT
+    # never gets set). Retry with backoff to ride out transient Hub outages.
     def build_images_once
       return if $IMAGES_BUILT
-      docker_compose "build"
+      attempts = 0
+      begin
+        docker_compose "build"
+      rescue RuntimeError => e
+        attempts += 1
+        raise if attempts >= 3
+        puts "compose build failed (attempt #{attempts}/3), retrying in #{15 * attempts}s: #{e.message.lines.first&.strip}"
+        sleep 15 * attempts
+        retry
+      end
       $IMAGES_BUILT = true
     end