feat: Integrate the dual-editor in vanilla-web-component

[fantonangeli]

Description

Integrate @openworkflowspec/dual-editor in examples/vanilla-web-component, replacing the direct usage of @openworkflowspec/diagram-editor.

Motivation

Validate that the Dual Editor can be consumed correctly from a non-React host and that the package integration works in the existing vanilla Web Component example.

Proposed Implementation

• Replace the direct @openworkflowspec/diagram-editor integration with @openworkflowspec/dual-editor.
• Update the Web Component wrapper and example as needed.
• Update the existing tests to cover the Dual Editor integration.

Definition of Done

• Implementation: Fully implemented according to the Open Workflow spec.
• Unit Tests: Comprehensive unit tests are included and passing.
• Integration Tests: Verified within the monorepo and target environments (Web/VS Code).
• Documentation: Updated README.md, ADRs, or official docs.
• Performance: No significant regression in editor responsiveness.
• Accessibility: UI changes comply with accessibility standards.