UIKit floats the Duo's tab bar 24pt above the bottom edge, below the
34pt safe area. The list's search field sat on the safe area, 10pt
higher, and the composer added its 6pt gutter on top, 16pt higher, so
the three bottoms differed.

The layout metrics observer now also reports UIKit's bar layout region
for a 48pt bar on the bottom edge (iOS 27.1), measured in each column.
On the Duo the search field and the composer pill end on it, level with
the tab bar, and the workspace list keeps its last row clear of the
field. Other devices keep their safe-area placement.

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