The conversations sidebar was force-shown via 'lg:flex' at large
breakpoints even when sidebarOpen was false, causing a broken split-
layout in the w-96 drawer panel (~144px left for actual chat).
Fixes:
- Sidebar no longer force-applies lg:flex in panelMode
- In panelMode the sidebar goes full-width and hides the chat area
entirely (stacked panel pattern instead of split-column)
- Hamburger toggle is always visible in panelMode (was lg:hidden)
- Selecting a conversation or creating a new one auto-closes the
sidebar in panelMode, returning to chat view
- Welcome screen and header title use compact sizing in panelMode
alex
a0bf8df221