Use when building, reviewing or fixing Svelte 5 (runes) and SvelteKit code — components with the rune primitives, rune modules versus stores, file routing, universal versus server load functions, form actions with progressive enhancement, remote functions, SSR/CSR/prerender choices, and adapters. Covers migrating Svelte 4 reactive statements to runes and hydration mismatches. NOT Next.js or RSC (that is `nextjs`).
