Request: Add an extra layer of permissions on the Agent Staffing Timeline so supervisors can edit the start and end times of existing events without being able to add new events or drag events on the timeline.

Supervisors need to adjust break and meal times, but broader editing access can lead to accidental duplicate events.

This would allow Supervisors to make routine timing changes independently, while admins retain control over event creation. This would help prevent duplicate breaks and meals and reduce schedule cleanup.