- add shared workflow template and serialization helpers for YAML, Mermaid, and DOT export
- add pattern-to-workflow upgrade and template application flows in AryxAppService
- persist built-in and custom workflow templates in workspace state and expose new IPC/preload methods
- cover the new backend slice with shared and app-service tests
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
