Undo and redo swapped the drawing but left the session on the current
layout's name. After undoing a rename or the creation of the current layout,
that layout no longer existed: nothing was drawn and commands failed with
"no such space". Now the session follows a renamed layout to its other name
(same tab order), keeping its paper view, and returns to the Model tab when
the layout is gone.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
