Token Lab: bidirectional code updates

[drwpow]

Description

The Token Lab should allow for token editing to update the code panel, and vice-versa.

Definition of done

• [ ] Invalid input should NOT sync either way, nor should it crash the app. Invalid JSON simply won’t update tokens. Likewise; invalid token updates won’t update JSON.
• [ ] Errors are surfaced either in tokens view, or code, and syncing resumes once all errors are resolved
• [ ] Errors in code view should be visible even when code view is collapsed (via badge, etc.)
• [ ] Errors in tokens view should be visible if looking at a different group
• Performance is NOT a concern for this ticket (as long as it’s usable)