Astro adapter (islands + SSR handler)

[PAMulligan]

Goal

Ship an Astro integration so Claudius can be dropped into Astro sites as a client-side island with SSR-friendly setup.

Acceptance criteria

• @pmds/claudius-astro integration package
• <Claudius client:idle /> island component
• Endpoint helper for /api/claudius
• Example app in examples/astro
• Verified compatibility with Astro 4.x and 5.x

Milestone

v1.2.0