Selecting a workflow compiles it, materializes WorkflowStep rows (tagged and
hidden from the step manager), and writes their ids into the task's existing
enabledWorkflowSteps — the executor's read path is untouched. Re-selection
replaces prior steps with no orphans; non-linear graphs abort before any write.
New tasks inherit a project default workflow (settings.defaultWorkflowId) ahead
of legacy default-on steps. Adds task_workflow_selection table (migration 104).
No scheduler/executor/merger changes.
47a42994ed