v0.1.30-pre.83

preview: Under Staircase (Pro) a conversation now fills the pane on a desktop and in a browser, as it
always has under Classic and Ink & paper: the centred 820dp column the Pro desktop pack asked for is gone,
and the messages and the message box run to the pane's edges under every look. Nothing moves on a phone,
which never reached the column, and nothing else in the app changes. No migration: schema stays at 23, so
this preview opens the same account as pre.79 and later and an older build going back still lands at the
account picker.