rustybuns init: support Astro #200

Astro apps (astro in deps). @astrojs/cloudflare gives a Worker build; desktop and box need its fetch handler served under Bun, or a static build for output: 'static'.

rustybuns init infers rwsdk, TanStack Start and Vite (± React) today (packages/cli/src/glue/fit.ts). Anything else comes back as unknown, and codeSplitters' Rusty Buns panel marks the repo needs work, linking here.

Done when init detects it, writes a working rustybuns.config.ts, and build desktop plus deploy run on a sample app. Then move it to ready in fit.ts.