Epic: Milestone 2 - Edit a node

[lornakelly]

Description

Make the diagram editable, one node at a time. Select a node → edit just that node → the edit is written back into the workflow text at the node's location. The text re-parses and the diagram redraws. Per the ADR: the text stays the single source of truth.

Hard boundary: edits a node's own content only. Out of scope: adding / deleting / reordering nodes (that's Milestone 3).

Motivation

The diagram stops being a viewer and becomes and editor, every subsequent milestone builds on the node-scoped writeback from this Milestone

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.