Per-user layout lives in the new app_user.prefs JSON column, read via
/v1/auth/me and written via PUT /v1/auth/me/prefs/workbench. The
workbench gets an in-place edit mode (gear -> drag to reorder, x to
remove, tray to add back, reset/done). Reset stores empty prefs so
registry changes still apply; ids of modules the user can't currently
see are kept on save.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
