feat(site): rough in microsite and design system

[oddurs]

Problem

People who care about fast infrastructure need one page that explains liam. The project needs a visual identity it can reuse. Refs cairn item 0035.

Approach

• Site: Astro with static output in site/, shipping no JavaScript framework. The only script is a 612-byte inline one for the boot-trace replay. dist is 440 KB, of which 380 KB is self-hosted variable fonts, and the landing page is 17 KB gzipped.
• Design system:
  • three token layers: raw values, then meanings for light and dark, then components;
  • Stack, Cluster and Grid layout primitives, which accept only spacing-scale steps;
  • eleven UI components;
  • a /design page showing all of it in both themes.
• Copy: follows the roadmap, and decision 0051 for the zero-drop claim.
• Seam:
  • scripts/task lint runs astro check and build runs astro build, installing from the lockfile first.
  • CI sets up pnpm and Node from site/package.json and site/.node-version.
  • Dependabot watches /site.
• Astro was chosen over Next.js because a static build ships no runtime and is what liam itself will serve (item 0050).

Budget impact

None to liam. The site is a static build.

Look at this sceptically

• The roadmap section is copied by hand from ROADMAP.md and will drift until it is generated from cairn list --json.
• Spacing and letter-spacing are still literal values in some components. Only type values are tokens so far.
• There is no automated check at a real 400 px phone width, because headless Chrome stops at 500 px.
• scripts/task installs site dependencies on every lint and build. That's cheap when nothing changed, but it assumes pnpm is on PATH.

Checks

• scripts/task check is green locally
• The cairn item is updated, or there was none
• No attribution to an assistant anywhere in the commits or this description