A double-chevron button in the sidebar's brand row shrinks the menu to a
strip of icons, freeing workspace for documents. Icons stay clickable with
tooltips; section headers, the Task Manager submenu and the recent-projects
list disappear while collapsed; the inbox count survives as a badge on the
icon. Collapsible sections (Config, Dev) ignore their closed state while
minimized so their entries stay reachable. Persisted in localStorage.
