Catalog and coordinator execution

Bridge workflow dispatch and execution callbacks were removed in S5 (owner decisions a9f0e60e and 6cab5c63). Coordinators run tasks with scripts/heyaira-run.sh and record results with task_update. Historical workflow data remains readable; no migration or data deletion is part of this change.

Catalog definitions and session_start remain available for interactive context. The server no longer dispatches catalog-backed background workflows. See run a task for the coordinator procedure.