Use when building an Astro 5 content site in a touchstone repo — islands, zero-JS-by-default, .astro components, client directives, content collections, rendering modes, view transitions, astro:env. Triggers on .astro files, `astro`/`@astrojs/*` in package.json, astro.config.mjs, src/content.config.ts. For the interactive framework inside an island use the react/svelte/vue skills; language-level TS rules live in the typescript skill.
