Width: 240px (lg:block, slide-in mobile)
Brand strip: bg-neutral-950, white wordmark, gray-400 tagline
Item: px-3 py-2, rounded-md, text-sm/13
Active: bg-gray-100, text-emerald-700, font-medium
Hover: same as active
Icon: Heroicons outline, stroke-1.5, 18px
Section labels: uppercase, text-xs, gray-400
User chip: bottom, avatar (emerald gradient initials)