- Add executionMode field to WorkflowStep type with 'agent' | 'api' options and validation
- Extend TaskStore CRUD with execution mode support and validation for prompt/description
- Add API validation layer in dashboard routes for workflow step create/update/delete
- Enhance WorkflowStepManager component with inline editing, validation feedback, and improved UX
- Add comprehensive tests for store CRUD validation and API route validation
- Clean up dashboard styles by removing unused CSS rules and dead test assertions