Fix wait_for_workers to allow retry workers to finish before reporting

When Buildkite retries a job, the main queue is already exhausted from
the original run. A retry worker may find unresolved failures via the
error-reports fallback and start re-running them via the Retry queue.
But those tests are not in the Redis running set, so active_workers?
returns false and the summary's wait_for_workers loop exits immediately
on exhausted? — canceling the retry worker before it can clear the
error-report.

Fix: after the main loop exits due to exhausted?, if this is a retry
run (BUILDKITE_RETRY_COUNT > 0) and error-reports are still non-empty,
wait up to inactive_workers_timeout for retry workers to clear them.

Author: ianks

ruby/lib/ci/queue/configuration.rb

@@ -99,6 +99,11 @@ def lazy_load_test_helper_paths
         @lazy_load_test_helpers.split(',').map(&:strip)
       end
 
+      def retry?
+        ENV.fetch("BUILDKITE_RETRY_COUNT", "0").to_i > 0 ||
+          ENV["SEMAPHORE_PIPELINE_RERUN"] == "true"
+      end
+
       def queue_init_timeout
         @queue_init_timeout || timeout
       end

ruby/lib/ci/queue/redis/supervisor.rb

@@ -39,6 +39,23 @@ def wait_for_workers
             yield if block_given?
           end
 
+          # On retry runs (BUILDKITE_RETRY_COUNT > 0), the main queue is already
+          # exhausted from the original run. A retry worker may have found unresolved
+          # failures via the error-reports fallback and be running them via the Retry
+          # queue — but those tests are NOT in the Redis running set so active_workers?
+          # returns false and the loop above exits immediately.
+          #
+          # Wait up to inactive_workers_timeout for retry workers to clear error-reports.
+          # This prevents the summary from canceling retry workers before they finish.
+          if exhausted? && config.retry? && !rescue_connection_errors { build.failed_tests }.empty?
+            @time_left_with_no_workers = config.inactive_workers_timeout
+            until rescue_connection_errors { build.failed_tests }.empty? ||
+                @time_left_with_no_workers <= 0
+              sleep 1
+              @time_left_with_no_workers -= 1
+            end
+          end
+
           exhausted?
         rescue CI::Queue::Redis::LostMaster
           false