Reverts v1.6.1's max-md:hidden wrapper around RightRail. On mobile,
RightRail now renders as a fixed right-side drawer (w-[85vw],
max-w-sm) toggled by a new FolderTree button in the Session header.
- New useRightRailDrawer hook mirrors useSidebarDrawer (Context +
auto-close on route change).
- New MobileRightRailBackdrop component in App.tsx mirrors the
existing MobileBackdrop for the left sidebar.
- RightRail computes an isOpen synthesis: on mobile, reads the
drawer Context; on desktop, reads the persistent internal state.
The existing tree-load effect and open_file_in_browser
subscription share this plumbing via openRail / closeRail
helpers.
- The desktop floating chevron handle is hidden on mobile (the
Session header's FolderTree button replaces it).
- Session header gains a mobile-only FolderTree button after the
ModelPicker, calling toggle() on the drawer Context.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>