- Add terminal-state check in executeCreate(): reject blocked_by
referencing completed/cancelled/failed tasks with actionable error
- Add full validation in executeUpdate(): batch query via GetTasksByIDs,
check existence + team membership + terminal state
- Add GetTasksByIDs batch query to TeamStore interface + pg implementation
- Refactor: modularize gateway, skills store, and team tools into
focused files
- Update TEAM.md leader prompt: prefer delegation, plan full task graph
upfront, create tasks in order with blocked_by UUIDs
