Get current schedule label in a system

## What problem does this solve or what need does it fill?

When completing #23140, I need to know the current schedule label to execute the corresponding queues.

## What solution would you like?

1. Use a Resource, updated per schedule label.
2. Add an update command for each schedule.
3. In schedule_scope, extract the label and update the Resource.

Start by reading the work described in #23140 and the existing schedule_scope entry point. Compare the proposed Resource, per-schedule update command, and label-extraction approaches, then confirm that the current schedule label is available for executing the corresponding queues.

Written by the indexing model from the issue text.