Handle SvelteKit adapters properly

- with SvelteKit using bun as the package manager and builder does not mean to use bun as the runner
- the runner language is determined by the adapter, not the runtime used to build
- I can use bun to build a nodejs output, and vice versa
- and also: with adapter-static, it should use the nginx thing it does for astro

Stories:
- Right now, if I launch a SvelteKit app that uses bun as its package manager but adapter-node as its runtime, it tries to run the node bundle with bun which won't work properly
- Right now, if I launch a SvelteKit app that uses adapter-static, it assumes it's node/bun and runs it with that
- Right now, the deno adapter and anything else probably is broken in a similar way

Empieza rastreando el adaptador de SvelteKit y la detección del entorno de ejecución que se usan al lanzar aplicaciones generadas, y compáralos después con el manejo existente de Astro con nginx para la salida estática. La tarea estará completada cuando adapter-node use Node independientemente del gestor de paquetes o del builder, adapter-static use nginx y los demás adaptadores no se ejecuten incorrectamente con Bun o Node.

Escrito por el modelo de indexación a partir del texto del issue.