Interactive Mantine islands

Embed any Mantine component as an interactive island straight from Markdown. Each SSR-capable island is prerendered to static HTML at build time — so crawlers, no-JS readers and the first paint all get real markup — and then hydrated in place on the client for full interactivity. The browser-only ones — most community widgets, the native map, and any component library configured without SSR — mount on the client instead; the context menu, data grid and lightbox are prerendered like the built-ins.

Prerendering became the default in 0.4.0; islands: {ssr: false} (or a bare islands: false) opts out, which keeps the client bundle so islands still mount on load. That is not the same as building with --no-bundle or without the islands toolchain: such a build ships no client bundle at all, and island widgets do not render.