docs: add AGENTS.md with Cursor Cloud dev environment setup notes

[archie-mckenzie]

Summary

Sets up the development environment for this repository and documents it for future agents. The only code change is a new AGENTS.md; no existing content or app code is modified.

What was set up

• Root pnpm workspace deps (apps/content Fumadocs / Next.js 16 site) via pnpm install.
• Standalone scripts/ validation project deps via npm --prefix scripts ci.

Verification

Service	Command	Result
apps/content build	pnpm build:content	434 static pages generated
apps/content dev	pnpm --filter ./apps/content dev	Ready on :3000, pages render
scripts tests	npm test (in scripts/)	18 + 14 passed
scripts links	npx tsx validate-links.ts	372 files, all links valid

Browsed the running docs site end-to-end (landing page → CLI Quickstart → sidebar navigation between Guides/Reference pages); all rendered with real content and no errors.

Notes

• Two separate dependency roots: pnpm at repo root, npm inside scripts/.
• pnpm install reports ignored build scripts (esbuild, sharp); expected and non-blocking.
• No /docs index route — deep-link to a real page such as /docs/cli/quickstart.

docs_site_navigation_demo.mp4
CLI Quickstart page

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