Collapsible navigation for app layouts
A two-state sidebar that collapses to a 64px icon rail or expands to 280px with labels, category headings, accordion sub-items with tree-line connectors, and a profile section at the bottom. Items take an optional count badge; topSlot and footerSlot host consumer content that fades out while collapsed; and the floating prop renders the rail as a glass card inset from the viewport edges.