[ew] New editor toggle setting not persisted across .page → edit roundtrip

[mhaack]

When the new UI toggle (new editor) is enabled, the setting is lost after navigating to .page and back. Clicking "Edit" in the Sidekick redirects to /edit (old editor) instead of /canvas, and the localStorage item storing the preference is gone.

Steps to reproduce:

Enable the new editor via the UI toggle
Navigate to the .page preview URL
Click "Edit" in the Sidekick

Expected behavior:
The localStorage preference persists across the .page roundtrip
Clicking "Edit" in Sidekick redirects to /canvas instead of /edit
/edit will always redirect to /canvas if the localStorage preference is set