Rows, section headings and the Join action lose their pill, slab and border below 750px.
Room names take the section headings' type (12px, uppercase, 600, heading strength); hover and
focus underline them, the selected row is bolder and underlined, a press dims, an unread room is
at full strength. Over the scene a halo of the theme's surface keeps text, icons and dots legible.
The phone list no longer shows the Create Room and Join with Address entries (routes and the
prompt stay for wider screens). The portrait overhang band is now the header's min-height, so
the 58px row margin no longer stacks on the header.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>