feat(frontend): improve history detail and model list UX

Open model resources via row click, restyle history detail with
session/analysis panels and mock playback, and theme scrollbars
globally with navy light/dark tokens.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/components/layout/Sidebar.tsx

@@ -98,7 +98,7 @@ export function Sidebar({ collapsed, onToggle }: SidebarProps) {
         </div>
       </div>
 
-      <nav className="min-h-0 flex-1 overflow-y-auto overflow-x-hidden px-3 py-5 pr-2 [scrollbar-width:thin] [scrollbar-color:var(--hairline-strong)_transparent]">
+      <nav className="scrollbar-subtle min-h-0 flex-1 overflow-y-auto overflow-x-hidden px-3 py-5 pr-2">
         <div className="space-y-1">
           <NavButton
             active={pathname === "/"}