#3991 feat(website): replace the Rspress site with the agent-device.dev product site

Summary

Replaces website/ (Rspress) with an Astro + Starlight site, so agent-device.dev serves the landing pages and docs from this repo through the Vercel project agent-device-website (root website/, public previews).

• Hero: "Open-source device layer for agents.", one centred column with the install command, GitHub stars and npm downloads, and a session that ends in evidence. Header: star count and docs search (same Pagefind index).
• Every docs page has a text/markdown twin at /docs/<page>.md; check-doc-links fails a page without one.
• deploy.yml publishes redirect stubs for oss.callstack.com/agent-device/*; old .md and llms*.txt URLs keep content copied from agent-device.dev, and the deploy fails until that site serves them.
• Production loads today's trackers (Vercel Analytics, GA, Common Room). Templates is removed; /templates redirects home.
• Fallow now analyses the site.

About 140 files, above the size guideline; one PR keeps the cutover one step.

Cutover: promote this head to production, move agent-device.dev and www to agent-device-website, then merge.

Validation

At 56786ff (rebased onto main) all 24 CI checks pass, including Integration Tests and Coverage, after a dogfooding pass with agent-browser on the preview; the later commits only guard the redirect deploy. Locally: lint, astro check, the site build, check-doc-links and the Fallow audit pass; browser tests cover the docs search (lazy load, retry, results), the star refresh and its rate-limit fallback, and every page width from 390 to 1440 px. The refactored loop scene's frames and the docs HTML were checked byte-identical.

🤖 Generated with Claude Code