feat: Update auto-layout to handle containment (parent/child node sizing and positioning)

[lornakelly]

Description

Update the auto-layout logic to support containment for parent-child node structures. Extend the ELK configuration so container nodes are sized and positioned based on the child nodes they contain. The auto-layout engine should calculate the parent node’s dimensions and placement to properly wrap and align its nested children

Motivation

Ensure nested workflow structures are laid out clearly and correctly by automatically sizing and positioning container nodes around their children, improving both accuracy and diagram readability.

Proposed Implementation

No response

Definition of Done

• Implementation: Fully implemented according to the Serverless 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.