The dialog decided "open page only" from the page that was open when it
opened. If a teammate deleted that page meanwhile, the editor moved to
another page and Save captured that one instead. Compare against the page
open at Save; a ticked page that has left the canvas is read as saved.

Also brings the page number and footer spacing onto DESIGN.md's type
roles and spacing steps.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>