Adds a compact sidebar beside the file list with All files, Trash, Starred, and Storage. The top menu aligns with the page content while the account dropdown stays at the far right. Trash, Starred, and Storage have inline placeholder pages.
Makes the breadcrumb compact and borderless, matches its loading skeleton spacing, and prevents file rows from stretching to fill the viewport. Selected sidebar items keep their appearance on hover.
Validation: production build and TypeScript checks pass. Biome checks pass with three pre-existing unused-function warnings in the directory route. Vite reports its existing bundle-size warning.