Public playground and demo site

[PAMulligan]

Goal

Give prospective adopters a live playground (claudius.pmds.info or similar) where they can configure a theme, paste an API key, and watch the widget run against their own backend.

Acceptance criteria

• Static playground site (Astro or Next.js)
• Configurator panel for theme, system prompt, model
• Auto-generated embed snippet
• Deployed via Cloudflare Pages
• Linked from README and docs site

Milestone

v1.2.0