feat(site): phase 1 — the foundation

Astro 7 with the Node adapter, Starlight mounted at /docs, the token file, both
self-hosted typefaces, the layout shell, and the two build-time checks from §12.

The palette's gold and cyan are sampled from runic-emblem.png rather than
guessed, per §11: 494,059 opaque pixels binned by hue, each value annotated with
its measured contrast against the ground, and restricted rather than brightened
where a ratio fails.

- checkTokens.mjs fails the build on any colour literal outside tokens.css,
  which is what keeps §7's "recolouring is a file copy" promise true.
- checkFacts.mjs re-reads all 14 externally-sourced facts from their authorities
  over the Gitea API and fails on disagreement. It also enforces D13: no email
  address in the source outside brand-default/brand.json.
- Both were negative-tested; neither has ever been allowed to pass by default.

§6 asks for output:'server' with per-page prerender=true. Astro 7 expresses the
same runtime shape as output:'static' with an adapter, opting individual routes
out — so the default is static rather than accidentally server-rendered.

Co-Authored-By: Claude <noreply@anthropic.com>

src/content.config.ts

@@ -0,0 +1,16 @@
+import { defineCollection } from 'astro:content';
+import { docsLoader } from '@astrojs/starlight/loaders';
+import { docsSchema } from '@astrojs/starlight/schema';
+
+/**
+ * Starlight injects a root-level `[...slug]` route, so a page's URL is its path inside the
+ * collection. The extra `docs/` level below is what mounts the documentation at `/docs/`
+ * rather than at the site root, leaving `/`, `/features/` and the rest to the marketing
+ * pages in `src/pages/` — which win, being more specific than a rest parameter.
+ *
+ *   src/content/docs/docs/index.mdx           ->  /docs/
+ *   src/content/docs/docs/getting-started/…   ->  /docs/getting-started/…
+ */
+export const collections = {
+  docs: defineCollection({ loader: docsLoader(), schema: docsSchema() }),
+};