bug: Handles are not disabled in edit mode

[lornakelly]

Describe the Bug

When isReadOnly prop is false, you are able to drag handles in the diagram which is not desired behaviour

Steps to reproduce

1. Open storybook
2. Toggle isReadOnly prop to false on diagram
3. Click and drag a handle

Screen.Recording.2026-09-10.at.15.30.11.mov

Expected Behavior

You should not be able to drag handles as we are not implementing a drag/drop editing feature

Editor Version

No response

Platform

Web / Browser

Additional Context

No response