When a Simplekiq orchestration encounters an empty batch (e.g., when
guard clauses skip all child jobs in a step), Sidekiq Pro automatically
schedules a Sidekiq::Batch::Empty job to ensure batch callbacks fire.
However, this Empty job was being scheduled to the default queue instead
of respecting the child_job_options queue configuration.

This occurred because Sidekiq Pro uses the batch.callback_queue attribute
to determine the queue for Empty jobs, and Simplekiq never set this value.

This commit fixes the issue by:
- Exposing child_job_options as a reader on Orchestration
- Setting callback_queue on both orchestration and step batches when a
  queue is specified in child_job_options
- Passing child_job_options through the callback chain so it's available
  in multi-step workflows

Empty jobs will now respect the configured queue, maintaining queue
isolation for orchestrations that use child_job_options. Orchestrations
without child_job_options continue to use the default queue as before.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>