Release Empty State component with illustration slots

The Empty State component ships with three illustration slots (no-data, error, first-use) and composable actions.

Release notes

• <EmptyState /> with illustration, title, description, actions slots
• Ships with 3 neutral SVG illustrations, tree-shaken when unused
• Docs page with usage guidelines and do/don’t examples

An empty state is the first screen most users see — treat it as a landing page, not an afterthought.