Spike: Object and array editable interface & UX (design)

[lornakelly]

Description

Follow on from #238

Objects and arrays currently render as placeholders - an object collapses to {…} and an array shows only its item count - so there's no way to view or edit their contents from the side panel.

This spike is to design how objects and arrays are viewed and edited in the inspector, with UX that holds up for real workflows rather than trivial cases. Design should include examples of all tasks that are/have objects and arrays so it can be referred to easily during implementation and can be used as a basis to manually test as well as write unit tests

Motivation

Good UX is a first-class requirement for this editor

Proposed Implementation

No response

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.