The previous search slot used UIKit's button form, and UIKit moved that
button out of the sidebar toolbar into the top of the detail column's
vertical bar. Holding the item to horizontal bars did not stop it.

UIKit's integrated field form stays in the sidebar's bottom toolbar:
full width, focused in place, and cancelled in place. Folded, search
keeps UIKit's own placement because the workspace tab bar owns the
bottom of the vertical bar there.

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