feat(workflow): shared types and collab-model support for Form View #8015

Task Summary

Give the frontend the types and shared-model hooks to load a workflow into the same live collaborative graph the canvas uses, so Form View edits the real workflow, not a copy.

• common/type/workflow.ts, workflow-metadata.interface.ts: add the form-binding types (FormFieldBinding, FormFieldOverride, FormBindingConfig), a DefaultView enum (CANVAS | FORM), and the defaultView workflow-metadata field
• WorkflowPersistService: setDefaultView(...)
• WorkflowActionService / shared-model.ts: form-binding state carried in the workflow content + shared-model support (coeditor cursor starts inactive until the mouse enters a canvas)
• agent-service: carry content.formBinding through an agent save untouched (opaque), so an agent edit can't blank the form

Task Type

• Refactor / Cleanup
• DevOps / Deployment / CI
• Testing / QA
• Documentation
• Performance
• Other