Phone viewports run the separate MobileApp shell (and a viewport crossing
now reloads into it), so the desktop layout's mobile branch was
unreachable: the drawer machinery, the full-screen secondaryView surface
switch (including the terminal/diagram desktop carve-out nothing could
trigger), the mobile header with its tab bar, the Cmd+number tab
shortcuts, the mobile quota panel, and the surface guard that reset
non-chat tabs. DrawerContext had no consumers left and is deleted.
Header drops from 2630 to 1853 lines; the desktop render is unchanged.
Bohdan Triapitsyn
8b7d7803de